In UI design education we tell the students: - differences in hue are best for differences in kind - differences in lightness or saturation are best for diffe

In UI design education we tell the students: - differences in hue are best for differences in kind - differences in lightness or saturation are best for differences in amount Ref.... Nault, W.H.: Children’s Map Reading Abilities. Geographic Society of Chicago, Newsletter, III (1967) Relating to op’s question It might be said that we perceive a rainbow ramp as a continuous thing. Hence it might work to visual a graduation in intensity. But from experience I can say that such maps are difficult to read. One problem is that a hue ramp has no terminals (such as black and white in the case of a lightness ramp).