The difference between Colour and non-Colour is more precisely expressed as the difference between chromacity and lightness. We must not forget that chromatic v

The difference between Colour and non-Colour is more precisely expressed as the difference between chromacity and lightness. We must not forget that chromatic vision developed after lightness vision. The former developed as response to the availability of fruit. Effectively, fruit and chromatic vision co-evolved. At a more experiential level, chromatic vision is an elaboration. It is not required, but in the lives of our ancestors, its presence signified the availability of a rare and pleasurable (carbohydrate intensive) experience. In design, this principle carries through. Colour is a layer that lays on top of the lightness experience.