Color blind

The way they test for color blindness is that they take a graphic composed of dots, some grey and some with a light, pastel version of the color in question. If the subject cannot distinguish between the lightly colored dots and grey dots, they are color blind for that color. Since most people can distinguish between the dots, it stands to reason to that color is a real thing and the color blind are not seeing the world accurately. Not that color blindness prevents people from living a normal life. Everyone is weaker in some colors than in others.

No Dre, I suspect 'em unable to conceive a color

Unless it can happen in a dream

I'd like to know how you propose to define what they are.