> If there's anything potentially scientific here, you could say that humans see three primary colors associated with the three cones -- red, green, blue -- an

> If there's anything potentially scientific here, you could say that humans see three primary colors associated with the three cones -- red, green, blue -- and therefore three intermediate colors -- yellow, cyan, magenta. By this measure, a rainbow would be 3 primary colors and 2 intermediate colors: red-green=yellow, green-blue=cyan. That's five. Magenta could be described as "not green" and thus does not appear in a rainbow.