CIE L*a*b*

A perceptually uniform colour space defined by the International Commission on Illumination (CIE) in 1976, where the numerical distance between two colour values approximates the perceived visual difference between those colours. The three dimensions are L* (lightness, from black to white), a* (green to red), and b* (blue to yellow). CIE L*a*b* is widely used in accessibility and colour science because its perceptual uniformity makes it suitable for calculating colour differences, evaluating contrast, and performing colour transformations such as simulating colour vision deficiencies or optimising recolouring for people with colour blindness.