Cromaticity

Chromaticity is an objective specification of the quality of a colour irrespective of its luminance, that is, as determined by its colourfulness (or saturation, chroma, intensity, or excitation purity) and hue.

In colour science, the white point of an illuminant or of a display is a neutral reference characterized by a chromaticity; for example, the white point of an sRGB display is an x,y chromaticity of [0.3127,0.3290]. All other chromaticities may be defined in relation to this reference using polar coordinates. The hue is the angular component, and the purity is the radial component, normalized by the maximum radius for that hue.