Colour-Coded for Your Convenience is fine. "Colour-Coded for Mandatory Gameplay Reasons" however... well, that's where it becomes a bit of an issue for games.
Not every single person on the planet can see every color in the visible spectrum, or at least, not properly. This is known as Color Blindness, and it comes in many flavors. Some have protanopianote , deuteranopianote , tritanopianote or the rarest of them all, monochromacynote .
To make games with color elements accessible to a wider audience, developers may implement a colorblind mode into their game via the settings (though even players with ordinary vision can freely select the option if they think it makes the game look better for them). It may affect either the entire screen's color palette, only the most vital parts of a game, or the game could add in symbols or patterns to its objects.
As you may expect, this trope is most commonly found in puzzle games that rely on colored objects, or games with Color-Coded Multiplayer that require you to know the color of what you're looking at, like distinguishing between abilities and team colors. Modern games studios started to commonly add color blind modes into their games in The New '10s and beyond, simply for the sake of accessibility, even if the game didn't really require such an option to make the game playable for those folks. In older games (even as late as The '90s), such a mode was sometimes implemented not with colorblind players in mind, but rather for players who didn't have color displays.
A very easy, and by far the most common way, that developers implement a color blind mode into a game is by overlaying a color filter preset on top of the game, which shows only specific colors to simulate different types of color blindness. The advantage of this is that it's good enough at replicating different colors for specific types of color blindness to get the job done, but the disadvantage is that color filters don't always work as expected, with certain colors still seeping through on occasion that could confuse color blind folks.
This also has the weighty advantage of game developers not having to manually adjust the colors for every part of the game. Part of the reason why modern 3D Games avoid recoloring the texture for color blind players is at least in part motivated by keeping the collective file size of a game down. In general, most 3D models in a given game have at least 3 textures associated to them; The Diffuse Map (that's the color and pattern you see) a Normal Map* (adds finer detailing to a model without modelling), and the Reflection Map (controls the reflection strength, go figure). A fair amount of games go even further to include other textures that control other functions (Occlusion maps, Specular Maps, Emissive Maps etc.), so as you might imagine, taken all together, any given model is gonna look pretty large if you also start to add six separate colored textures, which would lead to absurd file sizes for each model* , which is just unfeasible as a solution for most developers to add, not to mention the time taken to make and bake these colorblind oriented textures to begin with. In 3D games at least, color filters are here to stay.
Subtrope of Anti-Frustration Features.
- A Hat in Time has it in spite of there actually being no puzzles or tasks where seeing in color would be a necessity. Whether it means color-based puzzles were once intended but Dummied Out, or if Gears For Breakfast were just looking out for their color-blind fans is anyone's guess.
- Arcaea's Arc Notes are normally blue and pink, but a toggle changes pink Arcs to yellow. One track, "Red and Blue", features hints pertaining to its Arc colors; colorblind mode will change all references to "RED" to "YELLOW".
- The Atari 2600 had a color/black-and-white switch on the console, because black-and-white televisions were still fairly common when it was released. Exact effects depended on the game; Combat and many other early games switched to monochrome, while many later games ignore it.
- Battlefield 3 has a simple colorblind mode, originally exclusive to PC but later added to consoles. It makes teammates dark blue, squadmates yellow-green, and enemies dark red, plus it adds a black border to text and icons.
- Battlefield 4 has a complete selection.
- Off - Squad: Light Green, Team: Light Blue, Enemy: Orange
- Protanopia - Squad: Gray, Team: Purple, Enemy: Green.
- Deuteranopia - Squad: Purple, Team: Indigo, Enemy: Salmon.
- Tritanopia - Squad: Purple, Team: Blue, Enemy: Orange.
- Battlefield 1 has similar options, plus neutral things are white. Also, there's a custom option allowing players to adjust it for whatever coloration they need.
- Blue Revolver has a few options to assist colorblind players, including reducing the background brightness and changing enemy bullet colors from pink and yellow to red and green.
- The original Windows port of Chip's Challenge has an option to switch to black and white graphics, since monochrome displays were still in use at the time. Keys, doors and buttons are given unique patterns, rather than colors.
- Crystal Crisis includes within its crystal colour sets a colourblind set that can be chosen, though it's anyone's guess how effective it is. It also includes an option to make a custom colour set for those unsatisfied with the one given to them.
- DOOM (2016) has its colorblind settings just filter the game to how it would look like if you had the disability rather than adjusting it to be more useful to such players, making them more suitable for challenge runs/curiosity than actual assistance, though it doesn't require hue recognition that much anyway (green lights often signify progress against many reddish backdrops, but they are glowing and thus still stand out well enough).
- Games in the Dots series (including Two Dots and Dots & Co) have a color blind mode which changes the color palette so that the different colors of dot are more distinct, and also marks each type of dot with a distinct glyph (red dots have a horizon line, green dots have a cross, and so on).
- The Game Boy port of Dr. Mario could be seen as this in comparison to its NES counterpart, albeit out of necessity due to console limitations. Rather than the NES that strictly uses color patterns the Game Boy uses both shades and patterns to differentiate between the pills, with them also appearing as hollow (yellow), checkerboard (blue), and solid (red) in addition to using different shades of green/grey. Undoubtedly there were color-blind fans who were very happy to learn that there was a version of this game they could actually play◊.
- More recently, a colorblind mod of Dr. Mario was made that changes the red / blue / yellow palette to a brown / blue / white one, making them distinguishable for people with most kinds of colorblindness, being only unplayable for people who have full monochromacy.
- Flow Free and its spinoffs, which normally have the user connecting same-colored dots, has a mode it adds letters to the dots. So instead of connecting dark-blue to dark-blue, you connect A to A.
- Final Fantasy XIV didn't have a color blind mode for years. Originally, the AOE markers were colored a dark red, which made it hard to see in dark areas or against certain surfaces. While this would annoy color blind players, it also annoyed players that weren't color blind. To alleviate the issue for both camps, the AOE markers were changed to a bright orange and pulsated. The game would eventually get a proper color blind mode.
- Fortnite has modes for protanopia, deuteranopia, and tritanopia, each of which can have a level which changes how strongly it's adjusted. According to players on Reddit, D10 also helps see through storm and T10 makes nighttime looks nice.
- FTL: Faster Than Light has an option for a colourblind-friendly interface, which adds status icons for enemy ship's systems that are normally colour-coded (a lock symbol for systems disabled by ionisation and an X for damaged systems), among other changes.
- The Polish puzzle game Kulki has a "mono monitor" mode, which desaturates the colors, apparently to make the game easier to play on a computer with a monochrome monitor.
- League of Legends has a colorblind mode intended for players with deuteranopia which has received actual use from regular players who prefer it. It changes allied health bars from green to blue, makes certain red effects yellow and green effects blue, and changes particle colors slightly.
- The Legend of Zelda: Link's Awakening: The 2019 Switch remake modified the Color Dungeon, adding square, circle and triangle shapes to all color-coded elements.
- Linx has a mode which gives a pattern to colored lines. Yellow lines lack a pattern, red lines are dotted, blue lines are striped vertically, green lines are striped diagonally, etc.
- The ZX Spectrum puzzle game Mam Plan has an alternate graphics mode, where the tiles were indicated not by colors but by patterns.
- Overwatch has three separate colorblind filters to simulate Deuteranopia, Protanopia, or Tritanopia. The game also comes with a slider to adjust the strength of the filter.
- Paladins has three separate colorblind filters to simulate Deuteranopia, Protanopia, or Tritanopia.
- Picross S5 has a "high contrast colors" toggle for Color Picross, which locks all cell colors to a fixed palette of easily-distinguishable colors.
- Piczle Lines has settings for protanopia, deuteranopia, and tritanopia, each of them changing the in-game palette to better suit the need. For example, tritanopia focuses on greens, blues, and violets.
- Colorblind mode in Progressbar 95 makes certain segments have characters mark them. For instance, dangerous red segments have an exclamation mark, or useless gray segments have a zero.
- Puzzle & Dragons has its colorblind mode make the water orbs darker, fire orbs brighter, dark squares less dark and more purple, light squares more yellowish, and the hearts go from pink to gray.
- Rodina features an option to turn navigational symbols for celestial bodies, normally rings distinguished by colour, into the initials of their names.
- Shovel Knight: King of Cards has a colorblind setting for Joustus. It makes the player's cards a much darker blue and the opponent's cards brighter orange than standard.
- Splatoon and its sequel have a "Color-lock" option, which locks the team colors to bright orange versus dark blue. While yellow and purple would likely be a better option thanks to the colors being the closest to black and white in terms of colorspace, orange and blue are the colors that appear most in the first game's marketing.
- The unreleased Game Boy and Game Boy Color versions of Sutte Hakkun would have contained a number of changes from the Satellaview/SNES versions to make it easier to tell apart the three different paint colors and their effects when injected into blocks without having to solely rely on color. Jars of paint use double-sided arrows that face either vertically (red), horizontally (blue), or diagonally (yellow), and the blocks they fill in are marked with stripes to indicate the direction they travel in.
- Team Fortress 2 has a colorblind mode that can be enabled in the options. So far, it just displays an icon over players that have been splashed with Jarate or Mad Milk for those who have trouble seeing the yellow tint or splash effect.
- Tetris 99 has an incidental example in the temporarily-unlockable Game Boy Tetris skin, which uses monochrome patterns on individual blocks to differentiate the seven tetriminoes, unlike the other skins which use colors. Downplayed, in that colors and block designs don't have any functional purpose in Tetris other than helping players see what the next piece is at a glance.
- Trainyard has an option to add letters to the colored trains and other elements that use colors. The letters used are R for Red, O for Orange, Y for Yellow, G for Green, B for Blue, P for Purple, and T for brown.
- This Very Wiki has one: The Highlight Links toggle in the Display Options. Turning it on gives page links a yellow highlight and an underline.
- World of Warcraft has a standard colorblind mode in the settings which for example changes money so that it isn't marked by colored coins, but by letters indicating which coin type it is (like "31g 41s 59c"), or marks recipes more likely to give skill points with plus signs. That said, hues can be adjusted for several forms of the disability, including the less talked about ones like achromatomaly. If you want a specific type, just type "/console colorblindshader #" in the chat with # replaced by the mode's number (0-8).