I'm pretty sure all of the colors combined would make some sort of poop-like color.
Black is a shade, as is white.

Actually black is all colors combined. The reason that black isn't in the rainbow is because a rainbow is fucking light dumbass. Black is the absence of light, not color.

It really depends on whether you're dealing with additive or subtractive color.

without light there is no color you dumbass

the color of something is dictated by what color of a light spectrum it reflects, since black is the abscence of color it reflects no light, thus absorbing it all and therefore it is the abscence of colors. white reflects all colors of the specturm and absorbs none, and so it is all colors put together. the rule applies for both light and color since light determines color

Not according to art, bro.