Colour is fascinating. Radiolab have produced some wonderful thought-provoking episodes on the topic – be sure to check out Colors and Why Isn’t the Sky Blue?

This Nautilus article by Mazviita Chirimuuta is in a similar vein:

Philosophers have a bad reputation for casting unwarranted doubt on established facts. Little could be more certain than your belief that the cloudless sky, on a summer afternoon, is blue. Yet we may wonder in earnest, is it also blue for the birds who fly up there, who have different eyes from ours? And if you take an object that shares that color—like the flag of the United Nations—and place half in shadow and half in the full sun, one side will be a darker blue. You might ask, what is the real color of the flag? The appearances of colors are frequently changing with the light, and as we move the objects surrounding them. Does that mean that the actual colors change?

Read the rest here.