I've set my balls to emit light. The one on the left emits red; the one on the right emits blue. Notice that my balls don't have their emissive color, but everything around them is illuminated by them. See how the red-emitting one has some blue shined on it and that the blue-emitting one has some red light shined on it. Look at the white ball above my head: see how it is illuminated red and blue by my balls and yellow by the setting sun.

See the full article: Glow, Full Bright, Shininess, and Light