I really don't know how the eyes work, too much mysteries to be discovered yet.
But I can play with mathematical functions and find one that matches what the eyes see. The functions even not need to be physically correct, the Phong model is one example, but if is simple and works then is ok.
Another mystery, why don't exist gray or brown lights, and how do we know what is gray and what is white?

Stupidity also evolves!