I was actually talking to an art professor the other day and he said that we didn't have a name for a color until we had a pigment. So the Egyptians had a concept of blue because they discovered a pigment to make it with but other cultures didn't have a name for the sky. So when you look at it that way the concept of what makes a color is formed is very vague. I mean to get one thing straight its more than possible that there are other types of spectrum of light we don't see its a fact. There's infrared and ultraviolet for example so that's established. This issue really is a matter of how visual processing works.