Color code

[1] 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.

[2] For example, playing card suits are multidimensional with color (black, red) and shape (club, diamond, heart, spade), which are partially redundant since clubs and spades are always black and diamonds and hearts are always red.

Adding color as a redundant attribute to a numeral or letter encoding in search tasks decreased time by 50–75%,[2]: Fig9  but in unidimensional identification tasks, using alphanumeric or line inclination codes caused less errors than color codes.

[2]: 18  Subjects reported the tasks as less monotonous and less inducing of eye strain and fatigue.