Do things look red, because they are red? Or are things red, because they look red? Naive realists would answer positively to the first question, and idealists positively to the second. But since Galileo natural scientists have provided a more radical answer: If there were no human beings, there would be no colors on the earth. To be exact, there are no colors in the objective world, and things in the world have no color. Colors are only subjective phenomena, like "hallucinations."