Why do we call people white when they demonstrably are pinkish. (Bill the collie)

For the same reason we call one type of wine white (or 'green' in Portugese) when in fact it isn't: Perception and in consequence language tends to increase (blow up) differences. And that goes back to the wiring of the neurons via lateral inhibition. And that..., maybe you didn't want to know it in such detail.

Wolfgang