any of three spectral colours (usually red, green, and blue) that can be mixed to match any other colour, including white light but excluding black

any one of the spectral colours cyan, magenta, or yellow that can be subtracted from white light to match any other colour. An equal mixture of the three produces a black pigment

any one of the colours red, yellow, green, or blue. All other colours look like a mixture of two or more of these colours and they play a unique role in the processing of colour by the visual system