Saunders and van Brakel's observation that “linguistic evidence provides no grounds for the universality of basic color categories” also applies to the concept of “colour” itself. The language of “seeing” is rooted in human experience, and its basic frame of reference is provided by the universal rhythm of “light” days and “dark” nights and by the fundamental and visually salient features of human environment: the sky, the sun, vegetation, fire, the sea, the naked earth.