(This article has been co-written with my colleague Jonathan Bailey)

Knowledge about color spans across several disciplines: physics, biology, psychology, art, and design. It is a useful tool for the artist to create emotion, for the game designer to emphasize function, and for the marketer to set apart. In this article we look at color in games – its function, how technology has improved color display, and how our biology affect the perception of color.

The Function of Color in Games

The primary function of color vision is to make it easier to identify objects, and indeed, the use of color in games reflect this. We make apples red in games because they are also red in the real world, and so we can recognize them easier in the game. But color has many other functions in games, as it does in art, design, and film. This section describe some of those.

Emotion

Color is a powerful way to evoke emotion.

The following is an example of essentially the same scene, with different colors. Each has a distinct mood.

Color grading is a popular method used (adapted from film) to adjust the colors of games in one sweep; usually with the purpose of changing the mood. Here is an example of an image rendered with different color gradings:

Sometimes, a color change can also be useful to reduce emotional impact. For example, to look less violent, some games color their blood green to pass certification requirements (such as those in Germany).

Branding and Fashion

Color plays an important role in the branding of games and making them instantly recognizable: the blue and orange of Portal, the bright red of Mirror’s Edge, the meaty red of Super Meat Boy, the purply blue from Super Mario Bros, the hot pink of Hotline Miami.

In addition to making games recognizable, color can also help convey its intended audience: for example, brighter colors are used more in casual games, while more nuanced colors are used in core games.

(Casual Games)

(FPS Games)

The choice of colors in games are often influenced by the fashion of the time. Below are samples of colors from the most popular of four different years, spanning three decades.

The year 2012 shows clear shift toward dominant blues and browns/oranges. Xaphan attributes the reduction of vibrancy (making games more homogenous and monochrome) to the pushing of realism and the use of shadows and atmospheric lighting. Many other games have purposefully used desaturation and tinting to achieve realism.

Visual Hierarchy

The elements of a game scene forms a natural hierarchy of importance. For example, the player, followed by enemies, followed by interactive objects, followed by background elements. Color can help make this hierarchy visually clear. In visual works, such as painting and film, this principle is used to guide the viewer’s visual focus to what is important. In interactive works, this is even more important, because it helps the player figure out what to do: where to go, who to attack, what to pick up.

Value, saturation and hue can all be used to distinguish important elements.

(Focus with value)

(Focus with saturation)

(Focus with hue)

Check out this guide for game developers on visual hierarchy.

Progression

Color can help give the player a sense of progression: a feeling of change of time or space. In Journey, for example, the change in mood goes hand-in-hand with change in color.

In Geometry Dash the backgrounds are in rainbow order, and it serves an additional purpose of making the game levels more distinct (this idea is discussed further under the section Content Variation below).

Mechanics

Some games exploit colors for new mechanics.

Exit Palette is a puzzle game with a color mixing mechanic. The goal is to get to the exit of each level by painting objects with different colors. Different colors give objects different properties (such as making them fly upwards), and by mixing the right color you can give objects the particular property needed to solve the puzzle.

Hue is a game where the player has to shift the hue of the world to make certain objects disappear.

The game DayZ has a color dye mechanic, where cloth can be dyed with dyes made from berries in the primary colors. By mixing berries in different ratios, secondary and tertiary colors can be obtained.

Some games make use of the difficulties in distinguishing colors for their mechanics. The color! is a game that asks you to find the square on a grid that is a different color, progressively showing more squares and closer colors. Specimen asks you to identify from a few blobs in a black petri dish the one that has the same color as the background.

Blendoku asks you to arrange a number of color swatches in gradient order in a crossword-style grid. Huedoku is the same idea, but in a grid. These games are similar to the Online Color Challenge which scores your ability to arrange four sets of color swatches in gradient order.

Brandseen is a game that relies on color memory (or brand recognition): players are asked to match the colors of popular brands by memory, and are given a score on how well they do it.

Signifiers and Identifiers

Colors in games are used to identify different elements and alert the player to properties of elements.

Identifiers

Color identifiers (also known as glyphs) are used to group and separate game elements, such as differentiating players, in game characters and in game areas.

(Age of Empires) 

A color glyph should be easy to label or mutually exclusive from other identifiers and neutral colors in the scene. Identifiers are commonly used in versus games like Kill Zone and territorial combat such as Rise of Nations.

(Kill Zone)

(Rise of Nations)

Signifiers

Signifiers are used to communicate properties of an element (such as an item or a section of terrain) to the player. The color of an item or area communicates whether or not it can be interacted with and how it can be used.

In Mirrors Edge’s runner mode, objects that can help you progress are highlighted in red.

(Mirrors Edge)

In the upcoming game Witness, special areas will be graded differently to mark their significance.

The excursion funnel in Portal 2 creates a blue portal for objects to be pushed through and an orange portal for objects to be pulled through.

(Portal 2)

Color is used to categorize different potion ingredients in the Pirates of the Caribbean Online (and many other games) depending on what they are made from.

(Pirates of the Caribbean Online)

Content Variation

Color variation is a cheap way to increase the content of the game.

In games with abstract art, levels have a tendency to look very similar, and it is easy for the depth of the game to be undervalued as a result. Changing the background color between levels is used to make levels more distinct visually, and give the player a better sense of the variety and depth in the game. Splice is one game that does this.

Some games, such as Tiny Wings and Blowfish Rescue, uses algorithms to generate endless color schemes. Here is an article that explains some basic techniques of generating palettes procedurally.

(Tiny Wings)

(Blowfish Rescue)

We have also built a Unity plugin, Colors to do this:

Color changes can also be used to get more content. Palette swapping (explained below) was a popular way to increase enemies and game items when space was still an issue. Today, changing colors is still a popular way to increase content. This technique is often used when the color also serves as a identifier.

Technology

Since the introduction of games on black screens with white and green graphics, the range of color displayed on devices has increased dramatically. This has allowed games to look more and more realistic.

Galaxian (1978) was the first game to use RGB colors. Up until then the only colors seen in games were produced using cellophane sheets and cardboard backgrounds.

Edit: It seems we were mistaken about the first color game! There were quite a few color games before this time. The exact history is a bit murky, but Wimbledon (1974?) and Color Gotcha (1973) are candidates. Galaxian may have been the first game that used multicolored sprites. In What Was The First "True" Color Arcade Video Game? Keith Smiths look at some of the first games that used color. (Thanks for Nicholas Ralabate who shared the link in the comments).

(Galaxian)

Edit The following paragraph was rewritten to fix some inacuracies. (Thanks to Mikie Simons for pointing those out.)

Some early devices that featured more than 256 colors were the PC Engine (1987) with 482 simultaneous colors (of a possible 512) and the Neo Geo (1990) with 4096 simultaneous colors (of a possible 65536. In 1994 Play Station set a new benchmark with 16.7 million colors.

Colour Lovers have a nice infogrpahic of the history of color in video games; a piece of it is shown below:

http://www.colourlovers.com/blog/2011/11/03/the-colorful-history-of-video-games-infographic-2

The color gamut of a device (such as a printer, television or LCD screen) is the portion of the color space that can be reproduced by that device. Most display devices render a scene using the three primary colors, red, green, and blue. The combination of these three colors allows one to display any color that is within the triangular region bounded by those three colors.

Advancements in technology have allowed devices to have larger and larger color gamuts, thus allowing games to display more and more color. A device that is able to reproduce the entire visible color space is an unrealized goal; but devices are getting closer. Some projectors uses more primary colors to increase the color gamut; for example, the Brilliant Color projector. The laser video projector uses 3 lasers to produce the broadest gamut available in practical display equipment today (about 90% of colors most humans can see), derived from the fact that lasers produce truly monochromatic primaries.

Old Techniques to Increase the Number of Perceptual Colors

Pallete swapping was used to increase art content in 8-bit and 16-bit color games, and to reduce the intense task of creating multiple 2D sprites. A simple method of increasing the variety of game characters and items is to reuse the same sprite, but use a different color palette.

Palette swapping was also used between different scenes in the game to increase the number of colors available. Before 3D rendering and full 32-bit true color games, palette cycling was used to animate water, fire and other environmental effects in games such as S.P.Y. Special Project Y. Color cycling involved using a single flat image and a 256 color palette (which was all video cards could render at the time). Visual effects (or animations) were produced by cycling between the colors of the palette, giving the illusion that pixels are moving.  

Dithering is a technique used to increase the apparent number of colors by interleaving pixels of different colors. For example, to get a yellow-green, a checker board pattern of green and yellow pixels could be used.  You can see the dithering in the screenshot from Aladdin below in the dunes and clouds.

Color Biology

Color is perceived by the brain as a result of light rays reflecting off objects and hitting the retina of the eye. However, different colors can have different biological effects and not all people see color the same. This can affect the player experience in many games.

One example of biological effects is how we see red. Red light focuses behind the retina which forces the lens to grow more convex to pull it forward. Therefore, we perceive that red areas are moving forward. This may explain why red captures attention and is exploited in games such as Mirror's Edge, or why warm colors give the impression of advancing when put next to cool colors. 

Color Blindness in Games

Color blindness, or color vision deficiency, is the inability or decreased ability to see color, or perceive color differences, under normal lighting conditions.

Color blindness affects about one in 12 men, and one in 200 women. The most common type of color blindness is Red-Green color blindness, which results in a difficulty in discriminating red and green hue. The below image shows colors seen with normal vision (left) and colors seen with Red-Green color deficiency. 

Although the majority of games don’t cater for color blind players, many are beginning to consider color blindness in the design process, by providing visual cues (shapes, text, patterns) other than color.

A common problem in first person shooter games are red and green indicators, which are used to distinguish opposing teams. A popular solution (implemented in Call of Duty: Black Ops) is to provide blue and orange indicators as an alternative. Treyarch went as far as having a color blind lead game tester.

This article gives some examples of what it is like to play games when you are color blind.

Impossible Colors

Impossible colors (or forbidden colors) are colors that, due to the functionality of the retina, are biologically impossible to be seen simultaneously. Impossible colors are not a mix of colors, but rather a hue that is similar to both, such as a hue that looks "redgreen" or "yellowblue".

Red light stimulates cone cells in the retina allowing us to see red, while green light inhibits cone cells causing us to see green. While most colors induce a mixture of effects from these neurons, red and green light cancel each other out, meaning we cannot perceive to see them from the same place. The equivalent happens for blue and yellow.

A number of experiments have been done to prove that impossible colors can indeed be seen. These experiments include using an eye tracker device or performing exercises to cause the cone cells to become fatigued. More recently the Oculus Rift has been used for games such as Diatomic Number to see impossible colors.

(Diatomic Number)