[Rick Lee]

I did this exact same science project in about 1981. I used four or five of those cheap aluminum condiment shakers, spray painted each one a different color, put a heat lamp in the middle of of a board, equidistant from them all, filled each with water and put cheap thermometers in each one. It was very crude, but painfully obvious what was going on. I think I got an honorable mention. The year before I built a periscope. Back then, they really judged you on how well you wrote up the explanation, not how elaborate your project was.

edit: ooops, just noticed you meant how each color absorbs light. I did mine on conducting heat.