Color determination depends on the instrument you are using to "see" it. A standard that everyone could understand would be using the human eye as the instrument. Given that the human eye can detect 256 different shades of each of the three primary colors, the number of colors that there are (not counting absolute white or absolute black- and we theoretically couldn't see absolute black because it reflects no light whatsoever, it'd be invisible) is 256 cubed, or 17,666,512 different colors.

An infinite number of shades of red? Only if you are using a spectrometer to "see" them. I can't "see" infrared waves with my eyes, so how do I know they are really red?!?

Bob