I found this demonstration of Newton's color wheel at Wolfram Demonstration project.
Newton proved that light is a combination of a seven colors spectrum (red, orange, yellow, green, blue, indigo and violet). I remember doing a color wheel in high school and it was a very interesting experience. The disc may have the right hues of the light, colours of the rainbow, and must be rotated quick enough to make our eyes not distinguish each one.
I cannot help to thing that white is a kind of illusion and if our eyes could see more quickly... well... I'm rambling.