|MadSci Network: Botany|
Yes, light color definitely affects plant growth. Natural sunlight contains the full visible spectrum, plus plenty of non-visible spectrum. When a plant is deprived of the spectrum of light on which it depends, it will suffer. The "Grow-Lights" available for plants are expensive because they have made sure to include all the important spectrum elements necessary for a healthy plant's growth.
Since Science Fair is probably coming up at your school, an interesting experiment would be taking one kind of plant, putting different specimens into different pots, and testing growth rate and health under exposure to different colors of light. This way, you can see for yourself, and wind up with a possible winning project.
Try the links in the MadSci Library for more information on Botany.