White is the absorption of all color, and if there is no color to absorb, then white would not exist. Black is the absence of color, but any black we can perceive has at least a little color in it, so as to what "black" with absolutely no color in it would look like might be similar to what blind people "see", otherwise I can't imagine what that would look like. Opacity, or clearness, is the inability to hold color, completely different from white or black . Knowing this, what it would look like depends on how color became nonexistent. If you were to make objects incapable of holding color, color would have no place to go, so become nonexistent,making the universe completely see through, but you still wouldn't see white because it wouldn't exist. If you were to remove all the color from the universe it would appear a shade of black incomparable to anything we have ever seen. If you don't have a headache by now, please tell me so and I'll explain the concept 1-D, 2-D, and 6-10-D.