Since colour only exists as the interpretation of the light which enters and is sensed by the eye, and the universe is mostly empty space which neither emits nor reflects light, the vast majority of the the universe can be said to be black, since this colour is the interpretation of the absence of light.
white is the universe, all colour you see is came from white,
if you want a proof, just draw 7 colour in a plastic plate and role it, you'll see white actually make 7 colours become one
Black is what we see since most of the universe has no light. Imagine if we could see all the radiation, cosmic rays, radio signals, etc. There would be a sight to behold.
Majority of it is black/ black matter... but the thing is color it depends on what is in that space of the universe certain particles or atoms give off certain type of light so it depends what kinda elements are present at the particular space.