how many different colors are there
I read somewhere that there are over 16 million different colors. 16 million is an estimate of how many different colors a 24 bit RGB computer monitor can simulate. This has no relevance to how many different colors the human eye can distinguish. Just as there are infinitely many numbers between 380 and 740 - including all of the fractions, of course - so there are infinitely many wavelengths between 380 and 740 nanometers - the visible spectrum of light. That doesn't even count the different tints and shades obtained by mixing in white, black, etc.