L*C*hab is the Cylindrical form of L*a*b*
space, where a*,b* have been transformed into a Chrominance value
and Hue angle in degrees.
Being derived directly from L*a*b* space, it has is a white
relative space, where the reference white has the L*C*h*ab
value 100,0,0. The typical assumption is that an observer is
adapted to the white reference, so that the L*C*h*ab
coordinates correspond to the colors relative to that white.