colours

Colours are the visual attribute displayed by light as perceived by the human eye and brain, commonly described in terms of hue, saturation, and brightness. They arise when light interacts with objects or materials and with the observer’s visual system, with the visible spectrum spanning roughly 380 to 740 nanometers. Objects appear colored because they reflect, transmit, or emit certain wavelengths while absorbing others; color perception also depends on illumination and the observer.

Colors can be mixed in two broad ways. In additive color mixing, such as on screens, red, green, and blue light combine to produce white; combinations of two primaries yield magenta, cyan, yellow, etc. In subtractive mixing, used in painting and printing, pigments absorb light, and the traditional primaries are red, blue, and yellow, though modern processes often use cyan, magenta, and yellow. The chosen primaries define the reproducible color range.

Color is captured and communicated through color spaces. RGB is used for digital displays; CMYK is used in printing. Perceptual spaces, such as CIELAB and CIECAM, aim to model how humans perceive color independent of device. Illumination conditions, measured as color temperature, affect perceived color and can cause metamerism, where two colors match under one light but not another.

Color vision deficiencies affect some observers' ability to distinguish certain hues. Cultural and commercial practices assign names and meanings to colors, and standardized systems (for example Pantone, web color codes) provide consistent references across devices and industries.