In the original Mobile Suit Gundam and in Gundam SEED, The Federation had blue uniforms for male enlisted personnel and pink for females (officers wore brown regardless of sex). Later in the series, Cagalli gets a pink Gundam of the same type as Kira's(Blue-On-White) first suit.
Cheery, perky Sailor Moon has pink, silver, white, or yellow hair in the original manga. Her predestined lover Tuxedo Mask has, depending on the image, dark black, blue, green, or purple hair. When he is married to Sailor Moon, he has pastel purple hair, which appears to be a symbol of his healing due to being with her. As far as costuming is concerned, though, Sailor Moon herself wears white and blue while Tuxedo Mask wears black and red.
Speaking of Sailor Moon, the original anime's Transformation Sequences for the Sailor Starlights involved the background and their bodies changing from blue to pink as they changed from their male disguises to their true female forms.
Even more ironic, the whole Tokyo Mew Mew team is female and all the aliens are male. In the final battle, where Ichigo blasts her final attack, and Deep Blue releases the Mu Aqua, you can clearly see a clash of pink and blue.
Anime hair color is all over the place; can't really associate any one color to a gender. The only exception is pink: guys will never have pink hair, ever. At least, I've never seen it. Probably due the whole "girls can wear pants but guys can't wear dresses" thing.
Shuichi begs to differ. Then again, he is the uke...
Mikage from Revolutionary Girl Utena has pink hair, as he is supposed to be a male counterpart to Utena and claim the position of Victor, while his companion Mamiya pretends to be a male Anthy. Although she isn't really pretending.
Natsu's one of the few true exceptions (though a character inferred it to be "red" in an early chapter—at least, according to some translations; in the manga, the darkest color it could be is "salmon pink", and in the anime, it's clearly pink). Some male characters in manga and anime DO dye their hair pink, however, such as Raikou, a BadassSamurai from Nabari No Ou, or Shima, an exorcist-in-training in Blue Exorcist.
A BL example are the title characters of Sukisho - with the uke having pink hair and eyes, while the seme has blue.
The Mu children in Toward the Terra have pink dresses for girls and blue jumpsuits for boys. The adults all wear purple.
In both the anime and The Movie, Speed Racer typically wears blue and white, while his girlfriend Trixie dons pink and red. However, on formal occasions in the anime, Trixie would wear a blue dress while Speed wore a red blazer.
Hayate and Hinagiku from Hayate the Combat Butler. It's especially noteworthy as it completely subverts the girly pink-haired girl/stoic blue-haired guy dynamic (just don't tell that to Hinagiku) as Hayate is quite emotional at times and is noted for being very girly while Hinagiku is generally pretty tough and acts more boyish. Like the above example, Hina proves that girly pink can be very Bad Ass and Hayate shows that being a slightly feminine Bishounen is also no handicap on that front.
Toyed with in the Slayers franchise in regards to the two model couples: for Lina and Gourry, the latter wears blue while the former wears a light shade of magenta. For Zelgadis and Amelia, the latter is a princess who has both a pink dress for diplomatic duties and a modest traveling outfit with some pink touches, while the former is a chimera who literally has blue (or blue-green) colored skin.
The Faceless Masses in Hidamari Sketch are often colored this way, whether they're hairless and limbless, shaped like restroom signs, or detailed in the outline but still a solid color.
Shugo Chara! has Nagihiko's Guardian Characters, the very pink and (sort of) girlish Temari and the very blue and boyish Rhythm. Also, Seiyo Academy's school uniforms follow the pattern as well, with the girl uniforms being red and the boy uniforms being blue.
Shows up frequently in Go Dannar with just about each of the couples/partners' pilot suits, noteably Goh and Anna. Even the more masculine of the two American female robot pilots were darker colors than her cohort (whose pink-and-white costume barely qualified as clothing).
Jessie and James of Team Rocket from Pokémon, though only in hair color.
Takuto and Meroko from Full Moon Wo Sagashite's anime. Takuto is blue and Meroko is red (in the manga she wears black) but she keeps the pink hair. Averts the trope of happy pink girlxstoic blue boy because they are not a couple, (no matter how much Meroko wishes it)).
The Game of Life board game is an example of this. Boy pegs are blue, girl pegs are pink. Interestingly, the rules say you have to put a second peg in your car when you get married, but they don't say what color the peg has to be.
The mutant twins Quicksilver and Scarlet Witch often wear blue and red costumes respectively, although Quicksilver's first costume was green.
Played with by Haruhi and Itsuki in SOS Pretty Cure; Shorttank Haruhi's theme color is actually red, and Ambiguously Gay Itsuki's is purple. Played straight with Mikuru and Kyon; Mikuru's theme color is pink, and while Kyon's theme color is a dull brown (it even shows in his Cure costume), his aura as a Cure is blue.
Played straight in Futari Wa Pretty Cure Dimensions by the very tomboyish Megumi Yamada and the somewhat effeminate Ken Ichida, who also happens to be the blue boy to another tomboy who likes pink—his own sister, Chiyoko.
In Rhythmic Pretty Cure, at the karate school Hitomi and Tsumugi go to on Mondays and Thursdays, the boys' karategi is blue, and the girls' karategi is pink.
In Harry Potter, Tonks usually went around with spiky pink hair. We don't see much of her son, Teddy in the books, but Fanon has largely agreed that his hair should be blue.
In one of the Xanth novels, the male and female main characters had switched bodies due to a magic spell gone wrong. When they manage to acquire clothes from a clothes tree, they take colors according to their mental gender, much to the confusion of their semi-sentient horse.
Stephen King's Dark Tower series features the sentient monorail Blaine and his 'sister', Patricia. They feature the reversed color scheme: Patricia is blue, and Blaine is pink.
In earlier seasons of Smallville, Lana always wears pick and Clark always wears blue.
Made fun of in an episode of The Fresh Prince of Bel-Air, where Ashley asks how they could tell from the sonogram if Vivian's baby was a boy or a girl.
Hilary: Oh, Ashley, you are so naive. If it's a boy, it's blue!
PinkRangers are always female. Blue Rangers are often male, but have been female a number of times. Out of the most common suit colors (Red, Blue, Yellow, Pink, Green, Black, and White), Green and Black (usually seen as interchangeable) are the only all-male colors (except in Kaizoku Sentai Gokaiger, see below).
Also, while the Pink Ranger is usually The Chick, more recent seasons have been subverting this (starting with Mirai Sentai Timeranger and Power Rangers Time Force, where Pink is the real team leader even if Red gets the official recognition). The most common inversion comes on teams with two girls, where Pink will be the level-headed Cool Big Sis while Yellow will be The Ditz.
Interestingly, this also extends to Kaizoku Sentai Gokaiger, where the Rangers have the power to assume the forms of their predecessors (complete with Distaff Counterpart costumes where necessary). Thus far, Pink Ranger Ahim is the only person to use any Pink Ranger Keys, while every other color has been used by people of both genders (except, again, for Green).
This is averted in the Gokaiger Vs. Gavan movie, where the whole team change into pink Sentai warriors.
LazyTown's two main characters fit this trope. Stephanie wears pink and Sportacus wears blue.
Lampshaded and played with in a stand up routine by Israeli comedian Uri Hezkiah. In Hebrew, almost every word grammatically has to have a gender, depending on who is spoken of or who is doing the speaking. Uri muses that since babies all look the same, the only way to know whether you should pick up your friend's baby and say "That's a cute baby boy" or "That's a cute baby girl" is whether it's dressed in blue or pink. He then says "But imagine you find a baby dressed in orange. What do you do? You can't risk offending your friend". After some thought, he picks up an imaginary baby and says "Why, that's a cute... organism!".
In one episode of the American version of The Office an employee brings her baby boy to the office (dressed in pink). Pam tells the mother "she's so cute" only to have her say he's a he. When Pam explains she thought the baby was a girl because of the pink clothing the mother responds with "Pink is his favorite color."
Take a close look at the icons used by Snopes sometime. For the categories involving urban legends centered on certain people, the males get an icon of a blue-haired boy while the females get an icon of a pink-haired girl.
The website Girls Ask Guys uses this scheme to differentiate between male and female users, by highlighting their username, their 'rank', and, if asking the question, their rating stars with the respective colour. If the user has not yet chosen an avatar, they sport a silhouette of their gender with the corresponding shade, too.
Inverted in BIONICLE. The females still retain the "pink" personality, but the majority of the female main characters are blue. And while there are no pink characters, the red ones are all male.
Fisher-PriceLittle People toys and playsets usually avert this, with characters wearing whatever they realistically would. However, Fisher-Price has started making all-pink sets. What makes this stupid is that they are simply recoloring old molds, usually ones with normal colors. So now girls can buy a pink (instead of yellow) bus or dump truck, and a pink (instead of white and blue) plane. And a pink house, which is identical to the normal house in mold, except pink. It's borderline condescending and, since the main difference between the two molds is one is entirely pink, completely insulting.
And not just Little People. If you look through the F-P toy line, you'll also see blatant examples of this. The Laugh and Learn Puppy plush comes in both "regular" and "pink" versions (where the only difference is that the plush fur and ears is pink- thankfully, they're fixing that- by giving Puppy a sister who has pink ears and likes the colors pink and purple). Heck, even their ill-fated PowerTouch reader system came in silver and blue for boys, and pink and purple for girls.
Many toys from V-Tech usually also fall squarely into this trope- many toys come in both pink for girls and blue for boys, and the only difference is the toy color. Other toys from the company tend to come in regular non-pastel shaded colors for boys, but still have a pink version aimed squarely at young girls.
Variant used in Leap Frog toys: Green for boys and purple for girls.
One of the three subspecies of Rath (including the general red/green variant), manifests itself in the Azure Rathalos and Pink Rathian.
In an inversion, the red-and-pink Teostra are male, while the blue Lunastra are female.
Bubble Bobble: One of the original two is the underdog Bob, who is a male human-turned-blue bubble dragon. His apparent partner in Bubble Symphony (in cutscenes, she is always beside Bob) is Coro, a female human-turned-magenta bubble dragon and one of the new group of two. Extended with green for Bub (a boy) and orange for Kulu (a girl), who are also beside each other in cutscenes.
Bubble Bobble Part2: In the NES version's intro, the protagonist who soon gets cursed wears (light greenish) blue, and the soon to be Distressed Damsel wears pink with a matching color bow.
Inversion: Male members of the Nidoran family are pink and purple. Female members are blue.
The shiny versions, however, play the trope straight (with the exception of Nidoqueen, whose shiny version is predominantly green).
Latias and Latios (twin dragons and legendary Pokemon) are red/female and blue/male, respectively.
Starting from the third generation onward, the font color on certain game menus (like the save screen) will be either blue or red/pink depending on whether the player character is male or female, respectively. In the fourth-generation games, the Poketch and the Pokegear are similarly color-coded.
Also, the text of NPCs in FireRed and LeafGreen will change color depending on their gender - red for girls, blue for boys, black for Pokemon and computers.
Professor Layton's young companions fit the trope. His apprentice, Luke, wears a blue hat and blue sweater, while his adopted daughter Flora wears a pink hair ribbon and either a white and pink (Curious Village) or pink and brown (the other games) dress.
This is the colour scheme most often given to Akari and Ricky in 1080 and Wave Race, those two being implied to be a couple.
In Golden Sun, all three pairs of villains (with the possible exception of Agatio, who looks more green than blue) are dressed like this. There's also Jenna and Piers from the second game.
In Resident Evil 2, the main playable characters are also color coded in this way, with Leon in a blue uniform and Claire in a pink 'biker' outfit.
In Twinbee, the blue Twinbee and the pink Winbee (which also has a heart-shaped cockpit) are piloted respectively by Light and his girl cousin Pastel, who wear the same colors as on their ships.
Twin Cobra II: Player 1's helicopter is blue and is piloted by a male, Player 2's helicopter is red and is piloted by a female.
Although he is associated with the color red because of his hat and shirt, Mario's outfit also includes blue overalls, and his love interest, Princess Peach, wears pink.
Command & Conquer: Generals has an.. extreme variation on this trope amongst the USA faction: Normally, the faction's superweapon is a blue Pillar of Light being reflected off a satelite to form a Kill Sat system. But play as the female general from their faction, and the beam turns a lovely shade of pink.
Said general is titled the "Superweapon General" however, so it is possible to handwave the color change as being part of some prototype technology.
Milla and Jude, the dual protagonists of Tales of Xillia are colour-coded this way, reflected in both their outfits and the colour of the game menu depending on which of their routes is currently being played. Inverted by the Big Bad Duumvirate, in a deliberate attempt to contrast them with the heroes: Muzet wears light blue and white to contrast Jude's dark blue and black outfit, and Gaius wears dark red and black to contrast Milla's pink.
Also inverted by Milla and Jude themselves in the sequel, where Jude wears a red shirt under his lab coat and Milla's white outfit has blue accents.
Used in VG Cats with Leo (who wears blue and has grey fur) and Aeris (who wears mainly purple-pink clothes and has pink fur).
Commented on by Millie in Ozy and Millie; one about her needing to 'staple pink frilly stuff' to herself to remind Stephan that she's a girl, and another where she thinks pink is a bit of a girly colour for herself. The pink here is her own skin after being hit with the defoliation Running Gag that Simpson had set up. As far as fur colour is concerned, Ozy is white-grey (Arctic fox), while Millie is red-orange (red fox). Make of that what you will.
Inverted in Fan Dan Go where a male character, Zephyr, has candyfloss pink hair, while his female compatriot, Sarin, has sky blue hair.
Used in Bittersweet Candybowl, where Lucy, the heroine, wears a pink ribbon, while Mike, the male hero, wears a blue scarf.
Used in The Princess: the title character, Sarah, seems to move about in a cloud of pink glitter and sparkles. Inverted as well, as her father is often seen in a pink shirt while her mother prefers blue. And something or other is being lampshaded, given that Sarah is an 8-year old transgirl and has recently changed her name from "Seth".
In Dorf Quest, boys are default black, girls are pink, gods are blue, and goddesses are purple.
Discussed in The Nostalgia Chick's analysis of the original ''Transformers'' cartoon, referring to both Arcee and Elita One. Elita One was the Distaff Counterpart of Optimus Prime, and so (leader/girl) pink to his (leader) red and (boy) blue coloring. Elita One's Amazon Brigade otherwise had nothing with the trope, her soldiers appearing in all kinds of colours. Arcee, being the one girl starting the third season, was pink, and so was her (intended) love interest Hot Rod in a magenta shade ("aging" to red when he became Rodimus Prime). From there, the trope gets interesting in that pink is a noticeable colour choice among the Autobot females, but also among the Decepticon males (though not much in the cartoon because that ended long before the toyline did). Hun-Grrr, Misfire, the Seacons, Skullcruncher, Spinister, Fangry, Gaihawk, Barricade, Roller Force, and Horri-Bull, among others, all sport a good level of pink. Blue is more equally divided between the factions.
In-universe. Butch Hartman had intended for them (or at least his hat) to be blue, but when his blue marker ran out before he could finish, he had to use a pink one instead.
In the episode of Pocoyo where he meets an alien, when the alien's parents turn up, the Narrator addresses the pink alien as the "Mummy Alien". The Alien then gives an angry look at the screen and the Narrator corrects himself, realizing it's the "Daddy Alien".
Blues Clues played it differently - Blue is blue and is female, but Magenta, who is pink, is also female.
In Tiny Toon Adventures, Buster is a blue bunny, and Babs is a pink one, and (even though they say that they're not related) sometimes they'll even break out matching props.
Yin and Yang from Yin Yang Yo are a pink bunny and a blue bunny respectively as well.
Flavio and Marita the hip-hippos from Animaniacs are blue and pinkish-purple respectively.
Because Disney dates to the early decades of the 20th century, the idea that blue represented calm, soothing, feminine attributes was still popular (with red/pink as the guy hero color). Due to this, many of Disney's early female characters from the first golden age are swathed in blue; Pink Girl Blue Boy would emerge slowly but surely much later on.
Minnie Mouse has been seen in many colors, but for most of her early color appearances, she was never seen in pink (pink colorations of old cartoons not counting). Merchandise and the comics would paint her whatever the heck they wanted; but blue was a color that she appeared in frequently. Best of all, the blue contrasted with Mickey's standard guy-hero red. The all-pink wouldn't emerge until the late Pluto cartoons, and the ever-famous red dress with white polka dots wouldn't come in until Disneyland was opened. In modern animated appearances, Minnie bounces back and forth the most between wearing soft blue to contrast Mickey, or bright red to match him. That doesn't stop marketing from dousing her home, her wardrobe, and her merchandise pink, of course.
The artists debated long and hard on what color SnowWhite should be dressed in, even testing out the (at the time) unusual idea to dress her in all pink, but in the end, they went with the easy-on-the-eyes blue bodice. Her prince, of course, brought the red cape.
The Blue Fairy from Pinocchio (and the only chick in the film, no less. Cleo doesn't count). This might be because in the original tale her name was the Fairy with Turquoise Hair. The blue becomes more noticeable, though, when contrasted with Pinocchio's red lederhosen (heeey, that's not Italian!).
Cinderella is debatable. Her dress is silver in the movie but blue in all follow-up merchandise in the Disney Princess line. The two dresses she wore as a child and her nightgown are blue.
Wendy from Peter Pan wore a blue nightdress, while her younger brother Michael wore pink pajamas.
In Lady and the Tramp, Lady has a blue collar, and Tramp gains a red collar at the end of the movie. Meanwhile, the baby in the movie is a boy, but his entire room and pajamas are pink.
Another dog example in 101 Dalmatians lies with Pongo, who sports a red collar, and Perdita who sports a blue one. It's not clear whether this extended to the puppies or not, since we only know the name and gender of three: Lucky, Rolly, and Patch, all males and all in red. In the animated series, there's definitely not a theme; Rolly and at least one other male (either Wizzer or Dipstick) had blue collars.
Tie-ins for this movie are notorious for getting this messed up. Often, Pongo and Perdita's collars will be switched, or some of them will be pink instead of red... actually, on the cover of the first VHS release, several of the puppies had magenta, purple, and even yellow collars.
The trend is shattered, though, in the late 1960s, where one would find girls popping up more frequently in purples and pinks (Shanti, Maid Marian, Bianca, Eilonwy, Megara, Esmeralda), girls wearing whatever the movie would require (Pocahontas in tan...but with a blue necklace), and then finally, girls who took both blue and pink/red in stride. Examples of pink-and-blue sharing being:
Aurora is a rare example from 1959. The three good fairies weren't sure how to color code Aurora, as blue was the traditional feminine color and pink was the emerging feminine color. Note how throughout most of the movie Aurora is wearing blue, but in the Disney Princess line she is always in pink. Hmmmmmm. Prince Phillip brings a red cape and hat to the party. Disney Princess-gear Aurora always wears pink because Cinderella always wears blue (Belle wears her yellow ballgown, and Snow White is a mixture of red, blue, and yellow). Aurora was changed over to the pink dress to get guests to stop mixing her up with Cinderella. Whether or not this problem truly arose in the Disney parks is not certain (of course, since so few guests seem to know who Aurora even is...)
Ariel had not just a blue dress, but a pink one as well. A portion of the fandom has since complained about the pink dress clashing with her aggressively red hair...but one must remember that it was the late 1980s (the tiles on the floor in that scene are black-and-white checkerboard. Natch). Notably, she wears a turquoise dress at the theme parks.
Belle is a more modern version of strictly blue; she wears blue throughout most of the movie, and it's what set her apart from the autumn-themed villagers. She also has a fancier pink dress which appears briefly once she and the Beast begin to get along. However, thanks to the Disney Princess line, it's a gold ball gown that she's primarily associated with, instead of her blue peasant garb. When Belle wears blue, the Beast wears a red cape. When she wears gold, the Beast is the boy in blue. Note that Gaston wears red.
There's a reason Belle wears that blue dress. If you pay attention, you'll notice that out of all the characters in that movie, only two wear blue.
Jasmine from Aladdin is another modern example of strictly-blue; but this might have been incidental, because throughout the whole movie Blue was Good and Red was Evil. Her Go-Go Enslavement outfit is red. Notably, Aladdin himself is associated with the color purple because he has both good and bad qualities. He's a thief but steals to survive, and shares with those even less fortunate than he.
Mulan's primary color is, believe it or not, green, that being the color of both her armor and the dress she wears at the beginning of the film. She has two outfits of different colors: the pink-with-blue-trim fancy gown she's forced to wear for her disastrous meeting with the Matchmaker, and a blue-with-red-trim dress she wears at the end of the film, when she defeats the Huns and proves herself. Shang also brought out a red cape...but this might've been due to the story's cultural setting.
Olivia, Jenny, Kida, and Captain Amelia carry on the grand tradition of strictly-blue-girls. Dr. Doppler, who Amelia hooks up with, is even kind enough to wear a red jacket next to her blue one. Aww.
In Fantasia 2000, Donald wears a red robe and Daisy wears a blue one.
Tiana from the The Princess and the Frog has earth-toned street clothes, but her main princess costume is blue. Her two wedding dresses are green, for obvious motif reasons.
Inverted in Cars, where hero Lightning McQueen is a red race car, while his love interest Sally is a blue Porsche 911 Carrera. Also inverted with two of the background race cars where the pink race car sponsoring Tank Coat is actually male, and the blue race car sponsoring Rev N Go is actually female.
Played straight with Finn McMissile and Holly Shiftwell from the sequel, however, as with the kissing couple seen on the bridge in Paris.
In the Pixar animated film A Bug's Life, all the female ants are pink, while all the male ants are blue.
A more recent straight example would be Tangled, where Rapunzel wears pink, lavender, and purple and Flynn wears blue.
Also inverted in Finding Nemo where we have Marlin, an orangey-red clownfish, and Dory, a blue regal tang.
In Dragon Tales, the main cast of dragons (assuming you count Quetzal as supporting) is certainly this way. Ord is blue; Cassie is pink. Zak and Wheezie, who are a two-headed dragon, are divided colorwise down the middle: the Zak half is green, while the Wheezie half is purple.
Parodied in Family Guy, where a talking blue car is hitting on a pink car but realizes that it's his buddy, whose owner gave him a paint job.
Though, at the last second of that particular Manatee Gag, it is implied that the pink car is gay/bi, at least.
Meg's clothes are pink and Chris wears blue.
In Hey Arnold!, Harold and Helga, who are the two main bullies of the fourth grade, are represented with blue and pink, respectively. However, Helga often calls Harold "pink boy" in reference to his ruddy skin tone.
Dottywot and Spottywot, respectively, in the British preschool series The Wotwots.
The first two cars to be crushed to death during the song "Worthless" from The Brave Little Toaster are actually a male blue car and a female pink car, respectively.
Gumball and Anais, the lead character and his little sister in The Amazing World of Gumball. The color motif is inverted with their parents, Richard and Nicole.
Regular Show: Mordecai is a blue jay and Margaret is a red-breasted robin (filling in for Pink).
Inverted and played straight with Charlotte in Making Fiends. She's a stereotypical, over-the-top caricature of everything adorable and annoying about the archetypal American little girl, but has baby blue as her color and motif. Still, she seems to love pink as much as expected, as almost all of her possessions are pink.
Rosie from Thomas the Tank Engine is a female pink tank locomotive. This is especially noticable when she is seen with Thomas, a blue tank locomotive.
In Gargoyles, the gargoyles' eyes will actually glow a different color depending on that gargoyle's gender: females' eyes glow red, while males' glow white. Inverted with the clones, however.
There's a good reason why all the females have glowing red eyes: originally, Demona was going to be the only red-eyed gargoyle, but since the show's writers did not want to make her role as the villain more obvious, they changed it so that every single female gargoyle has red eyes and not Demona.
Mr. Bogus wears a pair of blue shorts, while his less-recurring cousin, Bogetta, wears a pink dress.
Grojband has Corey Riffin and his evil older biological sister Trina Riffin.
Luvs once marketed pink and blue diapers for girls and boys respectively. The color-coding was more for the parents' convenience; the diapers' design differed between the ones for boys and the ones for girls: there was more absorbent material either in front (for boys) or beneath (for girls) depending on which one they were intended for. They don't do this any more, possibly for the manufacturer's convenience.
Huggies Pullups and other absorbent training pants, on the other hand, continue to be colored in pink and blue, because toilet training tends to coincide with the time when children develop gender roles.
This seems to have been a general thing of the nineties: both Huggies and Pampers (the two biggest brands in the UK) had this through all their range, with only newborn and prem size nappies in unisex green and white. Both dropped it later for single forms packaged in green, yellow or orange (possibly because new materials meant that they no longer have big pads of cotton wadding in them- like ladies' pads, they all now have a gel core).
Older Than Radio in Real Life (and well before most other Real Life cited examples of this): The following comes from historian Tamara Plakins Thornton in a book on the history of handwriting instruction. Because eighteenth- and nineteenth-century etiquette recommended teaching different handwriting styles to people of different genders and social ranks (so that one could tell at a glance whether a letter came from a woman, from a member of the lower classes, or from someone socially important), at least one author of handwriting textbooks for the American upper/midle classes color-coded the books by gender. "In 1845[,] writing master James French issued two copybooks, a Gentlemen's Writing Book, bound in blue, and a Ladies ' Writing Book, bound in pink. In the former, French's male students practiced their mercantile running hand [a script style used by 18th- and 19th-century American and English businessmen] ... while their female counterparts rehearsed the ladies' epistolary [a more delicate and ornamented writing style, taught to women and girls of the era instead of the styles considered proper for males] ... " Source: Handwriting in America: A Cultural History by historian Tamara Plakins Thornton, 1998, p. 43. This early American example of Pink Girl Blue Boy is apparently also the sole pre-20th-century example.
In the Netherlands, it's tradition for parents and older siblings to serve rusk topped with muisjes, little sugar-covered aniseed sprinkles, to visitors, colleagues, and classmates to celebrate a newborn. While initially only available in a pink/white mix, a blue/white mix became available in the early 90s and is now generally used when a boy is born. Since 1938, an orange/white mix has been created for a short period after a royal birth, and with the 'birth' of the new pope in 2005, some catholic institutions handed out rusks topped with yellow/white muisjes, though these were not widely sold in supermarkets, if at all.
In the 1920s, pink was deemed more appropriate for boys due to its close associations with red. Blue was assigned to girls since it was more “delicate and dainty” and had close ties to the imagery of the Virgin Mary. This practice continued until the 1940s, when the gender colors were reversed and became the stereotypes that we are still familiar with today.
Before this, babies were usually seen in white or undyed clothes- possibly to symbolise innocence, also possibly because families in those days tended to be large and cloth was more expensive, so parents wanted clothes that would only be worn for a few months to be useful on all their children.
Just before this trope come into force, Jerome K. Jerome wrote an anguished (but very funny) article of how, now it was suddenly the social convention for babies to actually be brought out in polite company, it had given rise to the social minefield of randomly guessing what pronouns to use for 'baby', and the offence it caused if one got them wrong.
You can buy pink stocks and grips for a number of guns, including the AR-15 & AK-47.
Many restroom signs are pink for women and blue for men. This may even go as far as the restroom's wall color, and some bathrooms take it even further. Pink and blue toilets for their respective bathrooms, pink or blue sinks, pink or blue dryers/paper towel dispensers (although, thankfully, the paper inside is still white or brown), and yes, even pink or blue liquid soap.
The cere (the small patch of skin above the beak) of a male parakeet is blue. That of the female is brown.