What is the opposite of color
The opposite of color is complementary colors. Complementary colors are known to be pairs of colors that are of opposite kind in some color model. For more information, you can check on http://en.wikipedia.org/wiki/Complementary_color.
A shade like black white and gray
I think your question is a lot heavier than at first appears. In a dualistic view of the universe everything is supposed to have it's opposite. So it that is the case, in regard to your question: I have no freakin clue! Any takers out there?
I guess white because white doesn't have any color in it.
The only opposite to color is black - it is the absence of color.