Uniform changes of components in the L*a*b* color model aim to correspond to uniform changes in perceived color. So the relative perceptual differences between any two colors in L*a*b* can be approximated by treating each color as a point in a three dimensional space (with three components: L*, a*, b*) and taking the Euclidean distance between them. This Euclidean distance in L*a*b* space is ΔE (often called “Delta E”).