A color code is a system for displaying information by using different colors.
The earliest examples of color codes in use are for long-distance communication by use of flags, as in semaphore communication. The United Kingdom adopted a color code scheme for such communication wherein red signified danger and white signified safety, with other colors having similar assignments of meaning.
As chemistry and other technologies advanced, it became expedient to use coloration as a signal for telling apart things that would otherwise be confusingly similar, such as wiring in electrical and electronic devices, and pharmaceutical pills.
The use of color codes has been extended to abstractions, such as the Homeland Security Advisory System color code in the United States. Similarly, hospital emergency codes often incorporate colors (such as the widely used "Code Blue" indicating a cardiac arrest), although they may also include numbers, and may not conform to a uniform standard.
Color codes do present some potential problems. On forms and signage, the use of color can distract from black and white text. They are often difficult for color blind and blind people to interpret, and even for those with normal color vision, use of many colors to code many variables can lead to use of confusingly similar colors.
Systems incorporating color-coding include: