Colour Coded For Your Convenience / Real Life

Convenient colour-coding in real life.

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General

• Ancient Egyptian artists routinely depicted Egyptian males with reddish-brown skin, while Egyptian females were portrayed with golden-tan skin. This seems to have been symbolic rather than illustrative of how tanned they were, as even female farm-laborers were shown as pale, and indoor-working male scribes, as reddish-skinned.
• For similar reasons, some ancient Greek "black-figure" pottery has all male figures as black and all female figures as white.
• While United States dollar banknotes/bills are all green, most currencies make each banknote of a different colour to help distinguish them.^note American bills adopted a mild difference in color, although it's not nearly as easy to see as most other countries'.
  • Blue = 20 Euro, $5 Canadian, $10 Australian, $10 New Zealand, $20 Mexican pesos, $500 Mexican pesos (new; to avoid confusion with the 20 pesos bill, this one is longer and made of paper), ₽50 and 2000 Russian, 5 Soviet/Imperial rubles; Brazil has dark blue for $100 and a lighter one for $2, $20 Hong Kong
  • Brown = $100 Canadian, ₽100 Russian, $50 Brazilian (though nearly orange), $500 Mexican pesos (old), $500 Hong Kong
  • Green = 100 Euro, 5 Pounds, $20 Canadian, $100 Australian, $20 New Zealand, ₽200 and 1000 Russian (though significantly bluish), 3 and 50 Soviet/Imperial rubles; Brazil used it for $1 before it was put out of circulation, $200 Mexican pesos, $50 Hong Kong (and also old $10 before it was mostly switched out for purple bills made of plastic)
  • Grey = 5 Euro
  • Orange = 50 Euro, 10 Pounds, $5 New Zealand, ₽5000 Russian, $100 Mexican pesos, $1000 Hong Kong (nicknamed the "Golden Bull" in Cantonese)
  • Pink = $5 Australian, 50 Pounds, $10 Brazilian, $50 Mexican pesos
  • Purple = 500 Euro, 20 Pounds, $10 Canadian, $50 New Zealand, ₽500 Russian, 25 Soviet/Imperial rubles, $5 Brazilian, $1000 Mexican pesos, $10 Hong Kong (new, usually made of plastic)
  • Red = 10 Euro, $50 Canadian, $20 Australian, $100 New Zealand, 10 Soviet/Imperial rubles, $100 Hong Kong
  • Yellow = 200 Euro, $50 Australian, ₽10 Russian (with green highlights), $20 Brazilian (with yellow highlights), 1 and 100 Soviet/Imperial rubles
  • When Australia and New Zealand decimalised their currencies in 1966-67, replacing one old pound with two new dollars, the colors on the pound banknotes were reused on their dollar equivalents to ease the transition. For example, the blue £5 notes in each country were replaced with blue $10 notes.
  • Similarly to the US bills, Japanese bills have generally the same color, blue-on-tan, though they do differ in accents and highlights, with the ¥10000 banknote being more orangish, ¥5000 purplish, and ¥1000 greenish. The virtually suspended ¥2000 note had bluish accents.
• Fruits change colour depending on how ripe they are. This is thought to be why humans evolved colour vision in the first place. Additionally, women are less prone to colorblindness than men, and some women are able to see more shades of red than men are. They believe this is a holdover from the old caveman days when women were the gatherers and had to differentiate between "safe to eat" red berries and "highly poisonous" red berries.
• Any plant or animal that is lavishly colored is often a warning sign that it is highly venomous, poisonous, or dangerous in some other way and thus should not be messed with. The most infamous example being the Poison Dart Frog. Their colors may look pretty, but it's only to warn other predators that they'll be the last meal they'll ever eat.

Product Labelling

• Artificial flavoring in the U.S. tends to follow a set pattern somewhere between this and Tastes Like Purple for things that are flavored, such as Popsicles, fruit drinks, or candy.
  • Red = Cherry (sometimes Watermelon)
  • Pink = Strawberry
  • Orange = Orange
  • Yellow = Lemon or, less frequently, Banana (occasionally Pineapple)
  • Green = Lime or Mint, very occasionally used for Apple.
  • Blue = Blueberry or Blue Raspberry.
  • Purple = Grape (US), Blackcurrant (UK)
  • White = Pineapple, Coconut
• Cigarette packaging tends to follow a general color-coding scheme, although it's far from universal. About the only thing that's consistent across most brands is that if it's in a green or predominantly green pack, it's menthol.^note And even that isn't universal; Canadian brand Export A doesn't even sell menthol and uses green for its full-flavor pack.
  • Red = full flavor
  • gold or blue = lights
  • silver or white = ultra lights
  • green = menthols
    • Defied in Australia. Plain packaging laws, designed to discourage smoking, mean that all tobacco products are packaged in an unattractive brownish olive drab color.
• Dairy product labels:
  • In the US, Whole milk is almost always red. 1% milk is usually light blue, 2% dark blue. Skim milk is usually yellow. Half-and-half is usually purple. Chocolate milk is brown.
    Drew Magary: I buy milk for my kids at least twice a week, and we need greater cap consistency from the milk industry. Red is always whole milk. Light blue is always skim. But between that? CHAOS. Two percent can be ANY color, by God. If we don't get this settled via Congressional mandate, everything will fall apart.
  • In New Zealand (the world's largest milk exporter), whole milk is dark blue, low fat is light blue, and skim is green. Non-homogenised milk is silver, calcium-fortified milk is yellow or orange, and cream is red. Like the US, Chocolate milk is brown.
    • Even cheese is color-coded in New Zealand - cheddar ("tasty") cheese is red, Colby is yellow, edam is blue, mild cheese is light green, and mozzarella is dark green.
  • In the UK, whole milk is blue, semi-skimmed is green and skimmed is red.
• If you take a look at your local hardware store in the power tools section, you'll likely notice a whole rainbow of colours, usually associated with their own brand:
  • Ryobi=Neon green
  • Bosch=Dark green
  • Black & Decker=Orange
  • Dewalt=Yellow
  • Cotech=Blue
  • Milwaukee=Red
• Many screwdriver or plier sets have the handles color-coded by tool type (for example, all flathead screwdrivers will have yellow handles while all Phillips heads will be blue) so that you can tell what type of tool it is at a glance.
• Likewise, low-end sets of kitchen knives often sport color-coded handles, making it easier for non-professionals to tell the bread knife from the chef's knife when only their grips protrude from a wooden knife block.
• Scotch tape, while known for just their "sticky but not too sticky" tape, has multiple types of tape, all in similarly sized dispensers, but with different colors in their plaid patterns to distinguish them.
  • Green = Standard tape
  • Red = Heavy Duty/Packing tape
  • Yellow = Double-sided tape
  • Blue = Painter's tape
  • Purple = Gift wrapping tape
• Most moist snuff brands follow a certain pattern on their labels:
  • red (ranging into brown) for "Natural" or "Straight" flavors
  • green for Wintergreen flavors
  • blue for Mint and "Ice" flavors
    • One brand even has a "cool wintergreen" packaged with a bluish-green label. The fruit flavors offered by some companies tend to break this a little.
• Sweetener packets for coffee and tea are often color coded:
  • White = White sugar
  • Brown = Brown/Raw sugar
  • Pink = Saccharin (Sweet-N-Low)
  • Blue = Aspartame (Equal)
  • Yellow = Sucralose (Splenda)
  • Green = Stevia
  • Orange = Monksfruit extract
• Each day when wholesale baked-goods companies ship fresh bread products to grocery stores and supermarkets, they alternate the colors of fasteners (twist-ties or plastic tags) used to seal their bagged loaves shut. This makes it easier for stores' stock-workers to spot which (if any) loaves have been sitting on the shelves unsold for longer than a day or two, and replace them with fresh ones.
• Standard colors for Lay's potato chips:
  • Yellow = Classic
  • Blue = Salt & Vinegar
  • Green = Sour Cream & Onion
  • Orange = Cheddar
  • Black = Barbeque
    • Walkers, the UK version of Lay's, has green as the color for Salt & Vinegar. Blue is Cheese & Onion instead.
    • In Holland, Lay's Cheese & Onion is yellow while green is Bolognese; Classic is red and Paprika is blue.
    • Chipsy, the Egyptian version of Lay's, has red for "Salt" (the "classic" flavor), dark blue for Salt & Vinegar, and light blue for "tomato" (really ketchup). Yellow is taken by the cheese flavor (replicating Roumy cheese, the most popular flavor in Egypt), with a lighter yellow for "spiced cheese" (same, with spices). Also, barbecue flavor is replaced with charcoal-grilled kebab (but still in the black package).
• Wrapper colors for standard varieties of M&M candies in the US:
  • Black = Milk Chocolate
  • Yellow = Peanut
  • Beige = Almond
  • Red = Peanut Butter
  • White = White Chocolate
  • Dark Green = Mint
  • Light Green = Crisped Rice
  • Dark Blue = Caramel
  • Light Blue = Pretzel
  • Dark Purple = Dark Chocolate
  • Light Purple = Fudge Brownie
  • Dark Brown = Coffee & Peanut
  • Light Brown = Toffee & Peanut
• At US self-serve gas stations, pump handles for diesel fuel are usually colored green to distinguish them from standard gasoline. This is very important, as mistakenly putting diesel in a non-diesel car will ruin your whole day. And most likely your whole car. High-ethanol gasoline, meanwhile, tends to be marked with yellow pump handles to differentiate it from standard unleaded fuel; accidentally putting this into a non-FlexFuel engine isn't immediately and irreversibly harmful, but it's definitely not something you'll want to make a habit of doing, either.
• While no law in Mexico requires gas stations to use specific colors for their different fuels (as long as each particular gas station uses clearly labeled colors it's fine), chances are you'll see regular gasoline pumps colored green, high octane pumps colored red, and diesel pumps colored black. This is because these are the colors used in PEMEX fuel stations, which until 2018 held a state-controlled monopoly on fuel retail. These colors are well known enough that if you drive up to a gas station that doesn't use these colors (such as Shell or Akron, which label regular gasoline respectively with yellow and blue) and ask for "green" fuel, you'll be served unleaded gasoline.
• In the UK, unleaded petrol (gasoline) is normally on green pumps and diesel on black pumps, though you should always double check. Back when leaded petrol was available those pumps were red.
• In Indonesia, gas stations operated by Pertamina, the state-owned gas company, use an elaborate color-coding system on their nozzles for their pumps. Premium, the lowest grade gasoline and phased out in 2021, uses yellow, Pertalite uses white, Pertamax uses blue, Pertamax Green uses purple and green, and Pertamax Plus and Pertamax Turbo use red, though the former had been discontinued in 2017. Meanwhile, the fuels for diesel engines (Biosolar, Dexlite, and Pertamina Dex) use various shades of green on their nozzles. This also extends to the dyes used on the gasoline fuels, though Pertalite uses bright green instead of white.
• In US retail stores, video game consoles and their accessories are arranged by color-coded display:
  • Red = Nintendo
  • Green = Microsoft/X-Box
  • Blue = Sony/Playstation

Clothing

• Starting this trope off young, many maternity wards put light blue bonnets on newborn boys and pink ones on newborn girls.
• The "Hanky Code", a series of signals supposedly used to indicate kink and gender preferences in bars. The color of the hanky indicates the activity and the position of the hanky (left or right back pocket) indicates a dominant or submissive.
• The "hoods" (more like shawls) worn by US college faculty at graduation ceremonies are doubly color-coded: the velvet collar's color indicates either Doctoral status or the wearer's field of study, while the interior fabric displays where the faculty member's own education took place.
  • In other countries, there's a whole world of other complexities - see the Other Wiki's page on Academic Dress in the UK for example.
• Some high schools colour code the uniform shirts based on student's ages [1]. See also the Degrassi example above.
  • Japanese schools do this with uwabaki shoes, with different color tips.
• State-owned public schools and Islamic schools (Madrasah) students in Indonesia wear white shirt with color-coded tie and pants or skirts. Elementary students wear red, junior high students wear navy blue, and senior high students wear bluish grey.
• Many street gangs have one or more colors associated with that particular gang. For example, Blue is used by Crips, La Eme/Sureños and Gangster Disciples (and theirFolk Nation affiliate gangs), while red is used by Bloods and Nuestra Familia/Norteños. Yellow is used primarily by Latin Kings. Wearing a rival gang's colors even as a civillian can be dangerous in active neighborhoods, and many schools in areas with a strong gang presence mandate neutral colors in their dress code.
  • Grape Street Watts Crips use purple as a symbol of their once truce between bloods and crips in the area. Other small Blood and Crip sets have their own local colors used alongside the main colors, including Black and Yelow, and Brown used by some Long Beach Crip sets, and Green used by some Blood sets.
• Women in the Kenyan Samburu tribe wear red clothing if they aren't married and blue clothing if they are.
• Catholic clergy have a somewhat elaborate color code for liturgical vestments (the actual clothing worn at Mass, as opposed to "clericals", the familiar suit-and-collar combo which serves as everyday wear for Catholic secular ^note  a regular diocesan priest, not attached to a religious order like the Franciscans or Dominicans priests^note Although the normal color is black for clericals, there aren't too many rules on it outside of "keep it humble", and so priests in hotter climes where black would be impractical often wear light blue or grey) that varies due to the time of year or the particular Mass being said.
  • Purple: Advent^note Late November until Midnight, December 24/25 and Lent ^note  Ash Wednesday until the Wednesday of Holy Week, as a sign of penance (though some have tried to differentiate between two different shades for the two seasons, the Church just says purple is the color). Priests also wear purple stoles while hearing Confession or administering last rites. Purple is also often worn for funeral Masses, as well as for masses with anointing of the sick.
  • White or Gold: Christmas^note December 25 until early January and Easter,^note  Easter Sunday and the 40 days following it, as well as on feasts outside of those seasons honoring Jesus, Mary, feasts or commemorations of saints as well as All Saints' Day. White can also be worn for funeral Masses or votive Masses for the dead.
  • Red: Palm Sunday,^note Sunday of Holy Week, the last week of Lent Holy Thursday and Good Friday,^note but NOT Holy Saturday, however, as it is the only day in the liturgical year where no Mass is ever said, and so the priest technically wears no vestment on that day, though the USCCB calendar prescribes purple vestments if a grave necessity arises Masses on feast days of martyrs, Pentecost^note 40 days after Easter and confirmation Masses
  • Green: Ordinary Time ^note Early January till Ash Wednesday, again immediately after Pentecost up to just before the Feast of Christ the King in late November, unless the celebration requires another vestment.
  • Black: Rarely seen but valid option for funeral Masses, can also be used for All Soul's Day or any mass commemorating the dead.
  • Rose: Worn two Sundays out of the entire year: Gaudete Sunday^note The third Sunday in Advent. And Laetare Sunday.^note The fourth Sunday in Lent. The color is rose and NOT pink. Priests have been known to go to great lengths in homilies on those two days to remind parishioners of this.
  • Blue: Not approved by the Church, but sometimes worn anyway by priests during Advent (as a way of distinguishing it from Lent as above). In some countries,^note Spain and the Philippines being chief among them. it has been approved as a vestment color for feasts of the Virgin Mary (as blue is the color of the Virgin Mary)
• Some Orthodox churches also use a similar scheme^note The actual rubrics of the Byzantine Rite prescribe no actual colors outside of "light" and "dark." that in Broad Strokes is something close to the following:
  • Gold for normal Divine Liturgies where there is no specific commemoration to the day;
  • Light Blue for feasts related to the Virgin Mary as Theotokos;
  • Purple for Sundays in Great Lent;
  • Red for commemorations of martyrs;
  • Green for Palm Sunday, Pentecost and certain saints;
  • Black for weekdays during Great Lent;
  • White for Pascha^note Easter, Nativity and other feasts commemorating Jesus, as well as funerals.
  • Rust/orange, used for two specific feasts, exclusive to the Russian Orthodox Church.
• Other Christian denominations that have a liturgical tradition (Anglicans, Lutherans, etc.) use broadly similar colors to denote their particular liturgical seasons.
• Some brand of hospital scrubs put a different color along the back of the neck of scrub tops, to make it easier to grab the correct size at a glance.
• In the community of Rajneeshpuram, populated exclusively by the cult of Indian guru Rajneesh, everyone wore an outfit entirely of red. This made it easy to distinguish between the cultists and the local townsfolk of Antelope, Oregon, when friction developed between the two neighboring communities. Townsfolk even rallied around the distinction with slogans such as "Better dead than red!"
• Football hooligans often don't wear their team gear when engaged in hooligan activity, partly to protect the team's image and partly to make it harder for police to pick them out. They do however favor clothes in similar colors to their team color. In case of the Old Firm in Glasgow, Celtic fans often dress in olive green and Rangers fans in navy blue.
• In Punk and Skinhead subcultures, wearing combat boots with colored laces have their own codes, which are often regional. Black laces tend to be the neutral color.

Entertainment & Sports

• Children's toy xylophones use different-colored bars to make it easier for young musicians to pick out the notes they wish to play from their neighbors.
• Many mini golf courses give each player a different colored golf ball so that golfers don't get confused about who has which ball.
• Most sports teams have one or two colors associated with their logos/jerseys. In international competitions (The World Cup, Olympic Games), it almost always overlaps with National Colors.
  • For examples that aren't in the flag: the Netherlands are orange after the royal family (the House of Orange), Italy blue for its former royal family (House of Savoy), Germany uses the Prussian white harkening from imperial days (the House of Hohenzollern), Australia uses green and gold (based on the golden wattle, Australia's national flower), New Zealand have black following Maori tradition, and the Japanese football team wears blue due to superstition.
• In Elizabethan England, the actors on stage were color-coded - rather than wear costumes fitting the era/location the play was said to take place in, modern-day outfits of different colors were used to tell whether a person was a ghost, wealthy man, etc. This made it easier for less-educated people to understand what was going on.
• Instrument strings, depending on the instrument and/or manufacturer. For example, though there is no universal system, many violin string manufacturers color the ends of the strings closest to the fine tuners different colors to make it easier to tell which string belongs where during restringing.
  • D'Addario is notable for doing this with guitar strings. This is largely due to the way their strings are packaged: most brands sell guitar strings in cases that contain strings in their own individually labeled envelopes. D'Addario's guitar strings, on the other hand, are packaged in more environmentally friendly packaging that instead simply bundles the strings together without any envelopes. Therefore, they color the ball ends of the strings accordingly:
    • High e: Silver
    • B: Purple
    • G: Green
    • D: Black
    • A: Red
    • Low E: Bronze
  • Likewise, many guitar (and other instrument) pick brands usually use different colors to represent the different thicknesses the picks are available in.
• International auto racing, prior to the rise of sponsorship liveries in The '70s, although national colours are often still incorporated into these liveries, and are also usually offered on road cars.
  • Red = Italy, usually called Rosso Corsa (Racing Red). Still used by Ferrari and Alfa Romeo Sauber in Formula One. Maserati traditionally use a darker shade closer to mauve, while Lamborghini are more often associated with yellow or lime green.
  • Light Blue = France, usually called Bleu de France (Blue of France). Most closely associated with classic Bugattis, Matra, and Talbot-Lago cars.
  • Gray or silver = Germany, still often used by Mercedes Benz and Audi. German racing cars are thus known among fans as "Silver Arrows" (Silberpfeil in German).
  • Dark Green = UK, usually called British Racing Green, still used most prominently by Aston Martin and Bentley in racing. Most British sports cars will have the colour as a paint selection. McLaren are the exception to the rule, as they're most commonly associated with orange.
  • White stripes over Dark Blue or vice-versa = USA, often still available as an option on sports cars.
  • White and red = Japan
  • Yellow - Belgium
• Horse racing:
  • 1= red
  • 2= white
  • 3= blue
  • 4= yellow
  • 5= green
  • 6= black
  • 7= orange
  • 8= pink
  • 9= turquoise
  • 10= purple
  • 11= gray
  • 12= lime
  • 13= brown
  • 14= maroon
• The colored belt rank system in most modern Martial Arts sports was created in order for practitioners to tell who was at what level at a glance.
• Formula One tires use color-coded sidewalls based on their hardness.
  • White = Hard
  • Yellow = Medium
  • Red = Soft
  • Green = Intermediate (part-dry, part-wet)
  • Blue = Wet

Military

• The American Civil War is often poetically referred to as "The Blue and the Grey", referencing the color of the Union and Confederate uniforms, respectively. In reality, this distinction was not as clear. Some troops on each side wore the "wrong" color before the distinction was formalized to avoid friendly fire. Also, the Confederacy had difficulty affording grey dye and often had to resort to brown.
• Many military forces will have particular colors they are associated with (for instance, the Red coats that the British army wore for some time). In modern times, these colors can distinguish between branches of a nation's military or, in some cases, smaller branches within those branches^note  the United States Army, for instance, has certain color-coded bits on their service uniforms to distinguish members of the different corps; for example, the Military Police Corps wear green and gold, while the Signal Corps wear red and white.
  • During WW2, the Irish army's uniform color and helmet style were at the time similar to Germany's. With a serious possibility existing that the Germans would invade Ireland as an easier alternative to directly attacking Britain, having Irish troops patrolling a border with nervous British soldiers on the other side primed and ready to recognise German equipment was held to be too big a risk, and thus the Irish adopted British-style helmets and uniforms so they would be readily identifiable as neutral troops and not enemies from a distance by British soldiers.
  • The German military forces have since the 1920s utilized Waffenfarben ("corps color") as a border on shoulder boards or background on collar tabs to indicate the type of unit a soldier belongs to. Some of the colors have changed — infantry was white during WWII and is now green — while others, such as the red for artillery units, have remained unchanged since their institution.
  • On the flight deck of an aircraft carrier, where everyone has a very specific job and it's much too noisy to be heard, personnel wear different colored shirts denoting their job, be it fuel, maintenance, munitions, flight operations, etc. Some examples, as used by US aircraft carrier flight deck personnel:
    • White: Safety (includes medical personnel, who additionally wear a red cross)
    • Blue: Aircraft handlers
    • Green: Launch and recovery equipment operators
    • Yellow: Direct aircraft movement on deck
    • Purple: Fueling personnel
    • Red: Anyone that deals with explosives, including "Explosive Ordnance Disposal" — . Ouch. As if it didn't sound dangerous already.
    • Silver: firefighters in heat-resistant suits.
• On military ships, the colors of pipes indicate their contents. Common examples:
  • red = fire main (sprinklers/fire hose; can be salt or freshwater)
  • red with green stripes = firefighting foam (mixed with seawater)
  • red with blue stripes = firefighting foam concentrate (before it is mixed)
  • blue = potable water
  • yellow = fuel oil/gasoline
  • black and yellow striped = lubrication oil
  • purple = aviation fuel
  • green = salt water
  • gold = sewage
  • silver = hot things (usually but not always steam)
• Russians with Rusting Rockets takes it to the extreme with colour-coded undershirts. No, seriously. It started back in XVIII century when sailors traditionally wore striped undershirts (telnyashkas) and so did the naval infantry. Their stripes were either deep-blue or black. Everybody knows that sailors are badass and marines are even more badass, so when, after World War II, airborne corps were created, they received light-blue-striped telnyashkas. The first commander of airborne corps, Vasiliy Margelov, was a former marine, you see. Then, around the 90's, the idea got around that you cannot be badass if you don't have telnyashka, so various forces started to introduce their own colour schemes.
  • Navy: Navy blue stripes. Also, black stripes are worn unofficially by submariners and the Naval Infantry, including Naval Spetsnaz
  • Airborne troops (VDV), including GRU Spetsnaz: Light blue stripes
  • Border guards: Green stripes
  • National Guard^note Unlike its US counterpart, Russian National Guard is under federal command and principally an intervention force against domestic unrest, closer in its mission to Italian Carabinieri, French National Gendarmerie, or Chinese People's Armed Police (used to be the Internal Troops of the Ministry of Interior before the 2016 reform): Burgundy stripes
  • Emergency Control Ministry (Emercom): Orange stripes
  • Soldiers do not wear a striped telnyashka — their undershirts are white.
• Similarly to the Russian undershirts, the US Army and US Air Force have color-coded berets to differentiate between particular corps or specialties:^note or at least, the Air Force does for those people who have earned the right to a beret
  • For the US Army:
    • Green Beret for Special Forces^note Something that was adopted from the British, who used green berets for their Commando units during World War II.
    • Tan Beret for Army Rangers^note Formerly black berets, before the black beret was authorized Army-wide. This was highly unpopular because the black beret had been exclusive to the Rangers for nearly 30 years.
    • Maroon Beret for Paratroopers^note Another that was adopted from the British during World War II, beginning in 1943 when a brigade of American paratroopers were made honorary members of Britain's Parachute Regiment and issued British berets.
    • Black Beret for all other Army personnel^note Only in their Class-A Uniforms. For their battlefield fatigues, they wear camouflage patrol caps.
  • For the US Air Force:
    • Sky Blue for cadets at the Air Force Academy
    • Dark Blue for Security Forces^note Inspired by the black berets of the Army Rangers, who trained a cadre of Security Policemen during the Vietnam War.
    • Black for Tactical Air Control Party, Air Liason Officers, and Air Mobility Liason Officers
    • Maroon for Pararescuemen and Combat Rescue Officers
    • Scarlet Combat Controllers and Special Tactics Officers
    • Pewter for Special Operations Weather Technician^note How do the flyboys know what the weather will be like over their target? These guys sneak into enemy territory and get the weather forecast for them.
    • Sage Green for SERE (Survival, Escape, Resistance and Evasion) Specialists
  • For the US Navy (during the Vietnam War only):
    • Black for river patrol boat crews
    • Camouflage for the Navy SEALs^note Unofficial, but widely used by SEAL Teams in the field.
• Russians also have colored berets, generally of the same color as the undershirts. The VDV have sky-blue berets, the Interior Troops spetsnaz have red berets, the EMERCOM have orange berets. The black beret is worn both in the Naval Infantry and in OMON (riot police, mooks with barely a pretense for eliteness). MVD special forces, though, issue maroon berets as a distinction that has to be won in an exceedingly hard test.
• The WW2 German army colour-coded its soldiers in a very thorough Germanic manner. Epaulette, collar and lapel braiding advertised a soldier's arm of service at a glance. Nearly forty colours identified soldiers ranging from veterinary surgeons to assault engineers, but among the most common were white (infantry), red (artillery), pink (panzer arm, assault guns), russet brown (reconnaissance), and black (pioneers).
  • Said thorough Germanic manner had already been used by the United States Army (as well as the Confederate Army) in the 19th century, with light blue for the infantry, yellow for cavalry and engineers, red for the artillery and so on.
  • In the 18th century, it was typical for European armies to distinguish different regiments of the same arm by different facing colours (usually displayed on collars and cuffs of the coat) and button colours (brass or white metal). The Austro-Hungarian infantry used this system until World War I with a total of 28 different Egalisierungsfarben including a shade called meergrasgrün ("sea-grass-green", not to be confounded with meergrün "sea-green" or grasgrün "grass-green"). Most armies seriously simplified their system of regimental colours, however, for instance in 1881 the British infantry (other than rifle units) basically was reduced to four facing colours: dark blue for Royal Regiments (including Guards), white for English and Welsh regiments, yellow for Scottish regiments, and green for Irish regiments.
  • The modern German Army (Heer) and Air Force (Luftwaffe) continue the tradition, though with some changes in colour:
    • Red: artillery, general officers
    • Bright red: general staff officers
    • Maroon: NBC defence
    • Pink: armoured corps
    • Orange: military police (Feldjäger)
    • Golden yellow: army reconnaissance, air force
    • Yellow: signals corps
    • Green: rifles/light infantry (Jäger), paratroopers, armoured infantry (Panzergrenadiere), mountain infantry (Gebirgsjäger)
    • Middle blue: logistics corps
    • Dark blue: medical corps
    • Light gray: army aviation
    • Black: military engineers
    • White: military bands
  • Additionally, most members of the German Army wear a beret, which is also colour-coded though according to a different system:
    • Green: light infantry, armoured infantry, Army soldiers in the Guard Battalion of the Ministry of Defence, certain members of the mountain infantry
    • Maroon: paratroopers, army aviation, special forces
    • Black: armoured corps, Army reconnaissance
    • Red: Army air defence, NBC defence, military engineers, artillery, signals corps, military police, logistics corps, psychological operations
    • Dark blue: medical corps
    • Navy-blue: Franco-German brigade, officer candidates, I. German/Dutch Corps, Eurocorps, Air Force soldiers in the Guard Battalion of the Ministry of Defence, naval force protection (Seebataillon), clearance divers and frogmen, Air Force Regiment
    • United Nations blue: German soldiers as part of UN peacekeeping operations
• During the early 20th Century, the United States developed a series of war plans to outline what would be done in the event of a war with other countries. Some plans were more developed than others, depending on how likely the Yanks with Tanks thought war with that country was. Each belligerent was referred to by color for both brevity and diplomatic considerations - in time the plans themselves were referred to by color.
  • War Plan Black: War against Germany, specifically the German Empire. The most well-known involved a World War I What If? where France was defeated by Germany in Europe and the latter attempted to seize French possessions in the Caribbean or launch an attack on the East Coast - the plan involved heavy mining of the seas and concentrating the Atlantic fleet in New England.
  • War Plan Blue: The US. No, not a prospective revival of the Confederacy - these just covered normal preparation actions to be undertaken in peacetime. In all the war plans, the US was code-named "Blue".
  • War Plan Brown: Dealing with an uprising in the Philippines, at the time effectively an American colony.
  • War Plan Gold: War with France. Much of it focused on France's Caribbean possessions rather than going all the way to Europe.
  • War Plan Gray: Two different ones, depending on the time period. The first was a military venture in Central America or the Caribbean - not that unlikely given American intentions of keeping the Western Hemisphere under its lead (and out of Europe's) goes as far back as the Monroe Doctrine. The second was for an invasion of the Portuguese Azores during the early part of World War II - Portugal was officially neutral but there were fears that Salazar might allow Nazi Germany to use the islands as a base to launch raids in the Atlantic.
  • War Plan Green: Invading Mexico, specifically to help establish a pro-American government in case of civil unrest.
  • War Plan Indigo: Invading Iceland, something the US actually did in 1941 (before the US and Nazi Germany were at war) after the fall of Denmark in order to allow British forces to move elsewhere.
  • War Plan Orange: War with Japan. This was the most extensively developed and re-developed of the color war plans. While the main basis of it (mustering up the Pacific Fleet and confronting the IJN head-on with a large surface navy before moving on the Home Islands) became outdated with technological advances in submarines and especially aircraft carriers (before and after the attack on Pearl Harbor), elements of this plan was eventually incorporated into the US's strategy in World War II, such as the large submarine fleet that was to blockade the Home Islands (originally to buy time for the Pacific Fleet to mobilize, the subs ended up playing a key role in choking Japanese industrial capability) and not straying too far from land-based air cover (the "island-hopping" strategy).
  • War Plan Purple: A revision of the earlier War Plan Violet, updated to deal with potential Axis subversion.
  • War Plan Red: War with the British Empire – ridiculous as it sounds now, it was considered an unlikely but real possibility due to the UK's alliance with Japan, potential conflicts over the Empire's Caribbean holdings, lingering bad feelings over unpaid debts from the Great War, and the last whisperings of a desire to unify "English-speaking North America" that had existed since 1775. This plan was probably also influenced by Admiral William Benson, Chief of Naval Operations from 1915 to 1919, who strongly disliked the English. The largest components of the Empire got their own shades: Britain itself was "Red" (this included Newfoundland, which at the time was separate from Canada), Canada was "Crimson", India "Ruby", Australia "Scarlet", New Zealand "Garnet", and Ireland "Emerald". The bulk of this plan outlined a multi-front invasion and occupation of Canada while the US Navy blocked the Royal Navy from entering the Western Atlantic.
  • War Plan Red-Orange: A two-front war with both the British and Japanese Empires, which became a concern after two formed an alliance prior to World War I. It was considered a nightmare scenario for the US, as both would have brought very formidable navies on both oceans, and the planners concluded that fighting both aggressively at the same time would have strained resources too much and so felt it would be better to focus attacks on one while playing defense on the other - it further concluded that focusing on the Atlantic would be better. This idea remained when the US entered World War II with the "Europe First" strategy.
  • War Plan Tan: Military intervention in Cuba, at the time a US protectorate.
  • War Plan Violet: Actually a set of plans for the Latin American countries; revised as War Plan Purple in the 1930s.
  • War Plan White: Domestic disturbance and uprising with the United States. Much of this was developed with Dirty Communists in mind, though the plan got the most exercise in the 1932 Bonus Army confrontation in Washington. Elements survived as Operation Garden Plot, which was drafted in response to race riots that broke out in Detroit, Newark, and the Watts neighborhood of Los Angeles in the late Sixties - the operation was later used in the 1992 Los Angeles Riots and immediately following the September 11th attacks.
  • War Plan Yellow: War in China. Not necessarily with China (whether the Republic of China under Chiang Kai-Shek, the Communists under Mao Zedong, or any of the warlords running amok); rather it concerned itself mainly with defending American interests in Beijing and Shanghai.
  • Rainbow Plans: Various plans involving different combinations of hostiles, allies, and scopes of battle; quickly developed in 1939-40 after Nazi Germany took Austria and Czechoslovakia, signed a non-aggression pact with the Soviet Union, and invaded Poland.
    • Rainbow One: the US defends the Western Hemisphere down to 10º south latitude against Germany and Japan (with the aid of as many neighboring countries as possible), while the UK and France remain neutral. Preparations were made for this eventuality after the fall of France, but fortunately, the UK and the Free French forces remained firm until the Soviets and US became directly involved.
    • Rainbow Two: US is allied with the UK and France; they support them in keeping Germany contained while rapidly striking against the Japanese in East Asia. Became irrelevant after the fall of France.
    • Rainbow Three: Essentially War Plan Orange + Rainbow One; the US goes it alone against Japan while protecting its own hemisphere.
    • Rainbow Four: A scenario even worse than that of War Plan Red-Orange; the European Axis powers conquer the UK and France and seize their fleets, gaining naval supremacy in the Atlantic and enabling them to move against South America. The US immediately goes on a war footing, occupies all British and French colonial possessions and other critical locations in the Americas (with the help of Canada and the by-now terrifying South American countries), and fights off the Nazis while diplomatically stalling Japan as long as possible.
    • Rainbow Five: The US allies with the UK and France and holds off the Japanese while building up its forces; then it deals with the enemies in Europe before going after Japan. Completed in November 1941, it's pretty much what actually happened.
  • Colors were also assigned to various other countries that weren't the main focus of a specific war plan:
    • Brown: Dutch East Indies
    • Carnation: Manchukuo (the Manchurian puppet state established by Japan in 1932)
    • Citron: Brazil
    • Lemon: Portugal
    • Maroon: Italy (later changed to Silver)
    • Olive: Dutch East Indies and (later) Spain
    • Pink: The Soviet Union (later changed to Purple)
    • Rainbow: The League of Nations (before the development of the Rainbow plans)
    • Velvet: The Caucasus region (from an unfulfilled proposal to provide air support to the Soviet Union there in 1942)
• The German high command during World War II also had a number of war plans named after colours:
  • Fall Grün ("Case Green"): 1) A planned invasion of Czechoslovakia formed in 1937, made moot with the Munich Agreement; 2) a 1940 plan for an invasion of Ireland to coincide with "Operation Sea Lion" (the invasion of Great Britain). Operation Tannenbaum (a planned invasion of Switzerland) was also initially called Operation Green (Unternehmen Grün).
  • Fall Weiß ("Case White"): 1) The attack on Poland in 1939; 2) an operation attempting to capture Tito and defeat his army in Yugoslavia in 1943.
  • Fall Braun ("Case Brown"): 1) A plan for a joint German-Italian attack on France, abandoned in favour of Fall Gelb and Fall Rot; 2) a supplementary operation during the Battle of the Bulge.
  • Fall Gelb ("Case Yellow"): The attack on the Netherlands, Belgium, and Luxembourg in 1940.
  • Fall Rot ("Case Red"): The offensive in France through the Ardennes in 1940.
  • Fall Blau ("Case Blue"): First part of the 1942 summer offensive against the Soviet Union.
  • Fall Schwarz ("Case Black"): An offensive against Tito's army in Yugoslavia in 1943.

Government & Law

• Signatures on many formal documents and contracts are required to be signed in blue ink, to better distinguish them from copies which are rendered in black-and-white.
• In American politics, Blue is the color associated with the Democratic Party (liberal), Red with the Republican Party (conservative), and Green (or Yellow) with Independent or Third-Party candidates. Hilariously, this color scheme is completely arbitrary: it was invented by the NBC broadcast network during their coverage of the extremely-close 2000 Presidential election purely as a means of keeping things straight on their electoral map. In previous elections, both NBC and the other networks had randomly chosen which color to use for which party on their electoral maps, because both the Democrats and the Republicans officially used the same combination of red, white and blue as the nation as a whole does. But it's been pretty much adopted by the political parties involved ever since (you'll often hear of a solid Republican or conservative state referred to in discourse as a "red state", one with a more even mix as a "purple", etc.). Even more hilariously, this color scheme is almost the exact opposite of that of European politics, where Blue is associated with conservative movements and Red with social democratic, socialist and communist ones. The association of Red with communism had long existed in the United States as well, making it all the more amusing that it's now associated with the conservative Republicans.
• In Europe, where most of the older flags are just of one or two colours, republican and democratic movements had a tendency to use striped tricolours as their flags. The first such example was probably the flag of the Dutch provinces rebelling against Spanish rule in the 16th century, which is used to this day and is striped horizontally red (originally orange), white and blue. The abortive Belgian Revolution of 1788 used the colours black, yellow and red. The French Revolution combined the red and blue of the city of Paris with the white of the Bourbon dynasty, resulting in the vertically striped blue, white and red flag of today. As the revolutionary armies moved beyond the borders of France, they founded new republics with different tricolors, for instance, green, white and red in northern Italy (now the national flag of all Italy) and green, yellow and red in the Helvetian Republic (when that became Switzerland again, they reintroduced their old bicoloured flag). Other such "radical" tricolors were the black, red and gold (yellow) flag of the German revolution of 1848 and the red, yellow and purple (claret) flag of the Spanish Republic used until it was crushed in the Spanish Civil War.
• International political movements are often associated with specific colors. Although it can vary from country to country and from time period to time period, broadly speaking:
  • Red: the color of blood, passion, and revolution, Red is usually associated with populist, radical, and occasionally violent, political movements. Nowadays most commonly associated with Marxism and Organized Labour, but in the past a wide range of radical political movements claimed Red as their color (most famously the Red Shirts of Garibaldi's volunteer army).
  • White: color of purity and peace. Nowadays mostly associated with Pacifism.
    • Beginning in the 18th Century, White became associated with loyalist or monarchist factions during European civil wars, e. g. the white cockade of the Jacobites, and the white badges and flags used by Royalists during the French Revolution and by the "Whites" of the Russian Civil War. Hence, White becomes associated with the reigning monarch, and Red with the rebels seeking to overthrow that monarch^noteHowever, this is in part coincidence, result of the Bourbon dynasty's long association with the colour white (going back to Henry IV's white plume) and the fact that Czarist armed forces had been using white flags with a blue saltire since the Middle Ages, seeking the protection of their Patron Saint, St. Andrew. (Russia still uses this flag as its naval ensign.) (And yes, this is a colour-inversion of the Scottish flag, with the same meaning.).
  • Black: Politically, the color Black has a long association with anonymity, lawlessness, and "non-personhood." Where colors or patterns of colors would signify personal identity and political allegiance, solid black, as the absence of color, meant the absence of allegiance. As far back as the Middle Ages, "black knights" carried no family crest or color on their shields, symbolizing their independence (or simply concealing their identities). Beginning in the 19th Century Black was adopted by Anarchist groups: the color of no country or government. More radical Anarchists groups often also use Black in conjunction with Red.
    • Black is also the most common colour of the "street clothes" (whether the traditional cassock or more contemporary dark suit with Roman collar) of Catholic clergy and by extension is associated with Catholic and Christian Democratic parties in various European countries.
    • Black is also a colour strongly associated with Fascism, from the proverbial Black Shirts of Mussolini's followers and their British imitators to the black uniforms of the German SS.
  • Brown: After World War One, Brown became the color of Nazism. Nazi party officials and most of its organisations (except the SS and some youth organisations) wore brown uniforms - the first ones had been surplus army shirts intended for use on the Turkish fronts (note that the regular German and Austrian army uniforms in the war had been in different shades of grey). The Nazi party central office in Munich was known as the Brown House.
    • It should be noted that even when the SS uniforms changed colour from brown to black in 1932, the members of this organisation still wore brown shirts, as technically they were a branch of the SA.
  • Green: color associated with nature, Green is the color of most Environmentalist movements.
    • Green (along with black) is also associated with Islam in many places.
    • In Ireland it is often seen as the colour of Nationalism and Catholicism, as opposed to Orange, the colour of Loyalism and Protestantism.
    • As well as in Russia, where National Democrats used green and black flags and were called "the Greens".
  • Gold: the "color of money," associated with Free Market Capitalism, and sometimes, by extension, Libertarianism.
  • Purple: In modern European politics, Purple is usually associated with coalition governments, being a combination of Red (radical left) and Blue (traditional conservative).
    • Purple is often associated with royalty, as it was the color worn by Roman Emperors. By extension, Purple was also associated with the Catholic Church during the Middle Ages.
  • Pink: associated with LGBT and Women's Health movements.
    • In Organized Labour circles, Pink has negative connotations, being a lighter shade of Red and therefore associated with moderate or "soft" socialism. The epithet "Pinko" was coined during the first Red Scare of the 1920s to imply a person had socialist leanings without actually being a member of any organization or political group.
• The Québec student strikers of 2012 adopted the Red Square as their symbol against the 75% hike in tuition and in favor to the strike. As it gained in popularity both in the student body and the general population, other factions in the conflict tried to promote their own squares, with varying levels of success...
  • Some students wore the Green Square to show support for the hike and taking a stand against the strike;
  • Other students wore the Blue Square, which meant they were against the hike but were also against the strike;
  • At some point, columnist Richard Martineau suggested the Yellow Square, which meant that you would favor a smaller hike. It never caught on. In fact, the Yellow Square already had a significance before (though perhaps not publicized enough) as an anti-nuclear stand in the province of Québec.
  • As the conflict dragged on, some parents and teacher adopted the White Square, urging both the government and student unions to compromise with a moratorium on tuition hikes, until such time as we could discuss the matter with cooler heads.
  • When the government passed bill 78, which would restrict freedom of assembly, protest, and picketing, especially on or near university grounds, writer Normand Baillargeon suggested the Black Square (to be worn WITH the Red Square) in protest of the violent repression suffered by student strikers since the beginning of the conflict, and as a symbol of grief over the death of democracy.
• The paper bound into legal pads is traditionally yellow, making it easy to tell a lawyer's own notes apart from white-paper documents kept in the same briefcase.

Science & Technology

• Anatomical diagrams traditionally use red for oxygenated blood vessels, blue for deoxygenated blood vessels, yellow for nerves, and green for lymphatic vessels. Can give rise to Reality Is Unrealistic, as some would-be med students take these colors literally and are later shocked to learn that actual deoxygenated blood is maroon, lymphatic fluid is clear-to-milky, and nerves are white.
• Electrical components such as resistors and transformers generally follow a (rather complex) color-coding scheme - the more bands it has, in the case of the Resistors, the higher ohms its resistance is, and the individual colors are multipliers for the base number, as seen here.◊
• Many space-filling or ball-and-stick models of certain molecules will have certain elements given a specific color. Here are some examples:
  • Hydrogen = white
  • Carbon = black (because of its association with coal)
  • Nitrogen = blue
  • Oxygen = red (because oxygenated blood is bright red)
  • Fluorine = dark green
  • Sulfur = yellow (because its naturally-occurring mineral form is yellow at standard temperature and pressure)
  • Chlorine = light green (because it is light green at standard temperature and pressure—the very name chlorine comes from the Greek word for "pale green")
• Most stars:
  • O-type Stars = Blue.
  • B-type Stars = Bluish-White.
  • A-type Stars = White.
  • F-type Stars = Yellowish-White.
  • G-type Stars = Yellow.
  • K-type Stars = Orange.
  • M-type Stars = Red.
  • Brown Dwarfs = Maroon.
  • Neutron Stars = Purple.
  • Black Holes = Black.
• Related to the above, even the planets of our own Solar System are often identified and depicted by their colored appearances:
  • Mercury = Gray.
  • Venus = Yellow.
  • Earth = Green and Blue.
  • Mars = Red.
  • Jupiter = A mixture of colors varying from White to Brown, with a little Red for the Great Red Spot.
  • Saturn = Orange.
  • Uranus = Cyan.
  • Neptune = Aquamarine.
  • Pluto and other Kuiper Belt objects = Pink^note As of New Horizons' flyby. and Purple.
• One aversion in real life that's still played straight in fiction: Gemstones. While in real life geology, most types of gemstone come in a variety of colors, in fiction, they still follow a pretty set pattern:
  • Diamonds = Clear/White
  • Emeralds = Green
  • Rubies = Red
  • Sapphires = Blue
  • Topaz = Yellow
  • Amethyst = Purple
• The PC99 standard gave us the color-coded ports and plugs we all use today to tell the difference between identical plugs that go into identical sockets with different uses (e.g. headphone and microphone jacks, old PS/2 keyboards and mice, etc.). To wit:
  • Mini-DIN PS/2: Green is for your mouse, purple for keyboard.
  • 1/8" TRS: pink for microphone, blue for line in, lime green for line out (speaker/headphones). 5.1 surround-sound systems use black and orange for extra speakers.
  • DB-submini: teal for 9-pin serial, fuchsia for 25-pin parallel, blue for VGA video, yellow for 15-pin MIDI/game port.
• USB 3.0 ports are blue. USB 2.x and earlier are not. A yellow USB port is usually an Always On USB port, a non-standardized proprietary USB port introduced on Lenovo ThinkPads whose host machine has been designed to keep powered despite being switched off or in ACPI sleep state.
• Similarly, color-coded electronic components as well as electrical wires are so electricians can tell their power and tolerances, and what colors to put on a given installation respectively at a glance.
• The vast networks of pipes in the Google datacenters are colour-coded, similar to the shipboard pipe example above. Similar schemes are probably in use all around the world, with network and power cables as well as pipes. Anywhere there's a mess of cables or wires, someone is probably going to make use of this concept to help make things easier to manage.
• Some types of medication, particularly those that are to be taken on an on-again/off-again schedule like some birth control pills. It's easier for the person to take a pill every day than to try to remember how many days they have already skipped/still need to skip so the meds are packaged with placebos for the skip week; those pills are a different color to the actual pill.
• Adjustable temperatures, whether by a water faucet or an air conditioner/heater, usually come in two colors; red for warm/hot and blue for cool/cold.
• The mechanical keyboard industry uses some common colors to denote switch types^note for anything not in the list below, color schemes are often manufacturer-specific:
  • Brown = non-clicky tactile
  • Blue = clicky tactile
  • Red = linear
  • Black = heavier linear
• Before HDMI cables became the dominant video connector format, color-coded RCA plugs were commonly used to carry audio and video signals. The exact number and colors of cables tended to vary between different formats:
  • Composite analog video: Yellow.
  • Component analog video: Green for Y (brightness), blue for Pb (difference between blue and white), red for Pr (difference between red and white).
  • Stereo analog audio: White for the left channel, red for the right channel.
  • S/PDIF digital audio: Orange.
• Warning lights tend to be colour coded to show the severity of the problem being reported. An exhaustive guide is beyond the scope of this list, but generally speaking:
  • Green: System is active and working normally.
  • Yellow: System has failed or requires attention.
  • Red: System has failed dangerously - either something safety critical has failed or system has been damaged (or will be unless immediately shut down).
  • Flashing Red: Critical system failure or other extremely dangerous condition has occurred.
• Storage drive manufacturer Western Digital adopted the so-called "Western Digital Rainbow" to denote the intended use-case for the drive:
  • Green: "Eco-friendly" drives, meant to be lower performing goes to sleep at the earliest opportunity. Typically derided as the "bottom barrel" budget drive. Retired in the mid 2010s, rolling it into the Blue series
  • Blue: A budget oriented lineup. They may not perform the best, but they're serviceable for most people. Available for both hard drives and SSDs
  • Red: Meant to be used in network attached storage drives, which typically include features suitable to it such as 24/7 operation and using idle cycles to perform housekeeping tasks. Only available for hard drives. Because they're seen as more reliable and not that much more expensive than Blue drives, enthusiasts like to use these for their budget storage needs.
  • Purple: Optimized for DVR type use-cases, like recording from home security cameras. Only available for hard drives.
  • Black: Performance oriented drives, available for both hard drives and SSDs. The "Raptor" series used to be the highest performance tier, but it was retired in the late 2000s.
  • Gold: Meant to be used in data centers and servers with demanding I/O needs. Only available for hard drives.

Transportation & Urban Planning

• Maps of infrastructure beneath major urban centers use color-coding to distinguish power lines, communication lines, sewers, storm drains, subways, pedestrian underpasses, maintenance tunnels, and underground roadways or railways from one another.
• In the United States at least, anything to do with travel on roads (signs, lights, even paint on the road) is color-coded to connote a general type of information. Sign shapes have meaning as well, but the color typically gives an astute driver a first-glance idea of what is on the sign before they even read it.
  • Red: Stop. (Red traffic lights, brake lights, Stop Signs, Do Not Enter signs, etc.)
  • Orange: Construction. (Cones/barrels, temporary signs, detours, etc.)
  • Yellow: Caution/"Be alert". (Yield signs, the yellow light on a stoplight, Children At Play signs, crosswalks, etc.)
  • White: Informational/Regulatory. (Speed limits, turn-only lanes, lines between lanes traveling the same direction, etc.)
  • Brown: Recreational or Cultural/Historical/Educational. (Directions to museums, historical landmarks, tourist attractions, etc.)
  • Green: Geographical/Guide information. (Street names, exit numbers and locations, etc.)
  • Blue: Services. (Restaurants/lodging/gas near an exit, rest stops, hospitals, etc.)
• Many bus agencies organize their fleet by color, according to the service type.
  • Seoul:
    • Blue: Trunk routes, usually radial.
    • Green: Neighborhood circulators, primarily designed to bring riders to subway stations.
    • Red: Express routes.
    • Yellow: Orbital routes.
  • Los Angeles
    • Orange (Officially "California Poppy"): Local all-stop routes.
    • Red (Officially "Rapid Red"): Express Limited-stop routes.
    • Blue (Officially "Business Blue"): Non-stop routes, primarily using freeways.
    • Silver: Metro Liner Bus Rapid Transit routes; the Orange Line and the Silver Line.
  • Washington, DC
    • Red: Local all-stop service.
    • Blue: Metro-extra, limited-stop service.
• The Budapest Transport Corporation uses different colors for different types of vehicles. Both the vehicles are painted this color and the lines on the map are signified by it:
  • Yellow: trams
  • Blue: buses
  • Red: trolley buses
  • Green: local/metropolitan railways
  • Subway lines have their own colors (though this doesn't always apply for the vehicles themselves):
    • Metro 1: yellow
    • Metro 2: red
    • Metro 3: blue
    • Metro 4: green
• This is quite common for any metropolitan mass transit system that's extensive enough to have multiple lines:
  • In older systems where the lines originally had names, it's a bit of a tossup whether people use the colors to refer to the lines:
    • On one hand, the names stick in some places even though it would be easy to use colors taken from the system map. For instance, in Philadelphia, while the two main mass-transit routes are consistently colored (the Broad Street Subway is always colored orange, the Market-Frankford Elevated is always blue), even extending to the colors of the signage and the colors of the seats in the cars, Philadelphians almost invariably call them the "Subway" (or the "Sub") and the "El" rather than the Orange Line and Blue Line.^note In 2021, SEPTA announced plans to use a letters-and-numbers naming scheme somewhat similar to the NYC Subway; this is still in the planning phases, though. Also, this reflects usage in English; interestingly, Spanish-speakers in Philadelphia (a sizeable community) tend to use the colors—e.g. the "El" in Spanish is usually "la Línea Azul". Similarly, no Londoner would dream of calling any of the Tube lines by their colours, even though they have been coloured consistently on Tube maps since the 1930s (save for lines added since then, of course).^note Going alphabetically, it would be Bakerloo=Brown Line, Central=Red Line, Circle=Yellow Line, District=Green Line, Hammersmith & City=Pink Line, Jubilee=Grey or Silver Line, Metropolitan=Magenta or Purple Line, Northern=Black Line, Picadilly=Blue Line, Victoria=Aqua or Azure Line, Waterloo & City = Turquoise Line. However, nobody wants to do it this way, so it isn't.
    • On the other hand, in some places, the colors have successfully replaced the names in common speech (though some set-in-their-ways older riders might not have adjusted). For instance, any Chicagoan who calls the Brown Line the "Ravenswood Route" is definitely an old-timer.^note If they call it the "Ravenswood Branch" they might be an old-timer or they might be a CTA employee or railfan, since the trackage from Belmont to Kimball is still called that. However, that’s a technical term relating to the fixed infrastructure; everyone for whom "Mayor Daley" was Richard M. not Richard J. calls the service—the trains and their schedule—the Brown Line.
  • In some newer systems, the lines never had another name to begin with; the colors are the names. The Washington Metro is a prime example, as it was built from scratch in the 1970. The metro systems started in India in the 2000s-2010s also tend to use this nomenclature (e.g. Delhi, Chennai, Mumbai, and Bangalore).
• Everyone knows what traffic lights mean - red means stop, green means go, yellow means prepare to stop here as the light will soon be red. However, in many places, at least across the US, a fourth light is used - white. This indicates vehicle exemption - that an approaching vehicle cannot stop at this intersection and must be allowed to proceed regardless of whether its lane has a green light. Typically, this is for law enforcement or emergency services, but can also apply to trains that have to use tracks that happen to run through an intersection. The UK has two additional light states - Red and yellow simultaneously means "get ready to go” and flashing yellow (only on pedestrian crossings) means "proceed if clear or wait if not clear".
• Tampa International Airport originally color-coded its numerous airlines based on the location of the airside terminal in which they typically docked: airlines in the northern terminals (C and D originally) were assigned to red, while airlines in the southern terminals (B and E) were assigned to blue. Because elevator banks, parking lots, ticket counters, and baggage claim areas shared this same dual color system, it helped keep airline facilities grouped together, thus minimizing the amount of walking required of passengers to get from place to place. While the color system still exists today, it's more or less lost its original fucntion as airlines get shuffled around on a fairly regular basis; thus, an airline that docks in one of the more northerly terminals may still find itself assigned to blue, or vice versa.
• Saint-Petersburg's tram routes have a code of two lights as an addition to route numbers. Red, yellow, green, blue and white colors are used. While there are routes using the same code, they never intersect so they cannot be confused.
• Once upon a time, some cities and states in the United States, including the District of Columbia, rather than the black-and-white signs normally associated with the US Highway System (not to be confused with the Interstate System), used various colors on their signs with the goal to assist driver navigation, although the reasons for the colors varied from locale to locale: sometimes they indicated a particular route, sometimes they indicated the direction the route was going, and occasionally they seemed to be more or less alternates to the black-and-white signs. (Some states, such as Arizona, used colors on their state route signs as well.) Although most states only used colored signs for a handful of years in the 1950s and 1960s, the Florida Department of Transportation developed a system it used for decades. Each route was designated with a certain color, and while colors were reused (US 41 and US 98 did receive unique colors, orange and black respectively; US 98 essentially had an inverted version of the standard sign), no two routes sharing a color intersected anywhere in the state.^note  There was one exception, when the green US 192 was later extended to meet also green US 27. The color signs were eventually discontinued when the MUTCD^note Manual on Uniform Traffic Control Devices (for Streets and Highways) rules changed and the FHWA^note Federal Highway Administration forbade the use of highway funds to replace non-standard signs, although FDoT elected to produce the signs at its own expense for a few years afterward, with the final color sign posted in 1996. Images and more information available here.
• In Poland, hiking and biking trails. Hiking trails are always black, yellow, red, green or blue, while biking ones get more varied colors, like purple (and a bicycle symbol above the colored part of the sign).

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