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 add color blind modes into their games in The New '10s and beyond, simply for the sakes of accessibility, even if the game didn't really require such an option to make the game playable.
A very easy way of developers implementing a color blind mode 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 to get the job done, without having to manually adjust the textures of every given sprite or model in the game (which for modern 3D games, is often unfeasible as that'd require going through every single texture and make four to six types of it per model.). The disadvantage is that the filters don't always work as expected, with certain colors still seeping through that could confuse color blind folks.
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. Undoubtedly there were color-blind fans who were very happy to learn that there was a version of this game they could actually play◊.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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).