Different colored light actually does have a profound effect on plant growth. Plants are green because they are absorbing all the colors except for green, so they reflect green. That means they are absorbing red and blue, like you were going to test in your project. Blue is the color with the smallest wavelength. These wavelengths help the plant with the photosynthesis process and producing food from light, water, and carbon dioxide. The longer wavelengths of red help the plant with towering through light-induced changes in the plant’s pigment, which is called phytochrome. So yes! Your experiment with the different colored bulbs would be most effective!

My ex-husband's sister won a science project prize by growing plants under different colors of cellophane. I'll suggest seeds in 4 or 5 small pots, with several seeds in each pot. After the seeds sprout, put a cover over each of them with some color of cellophane [or plastic that lets some light through] - maybe red, green, yellow, blue [or any 3 of those] and, over the last pot, clear cellophane or a clear plastic baggie with some holes in it, to serve as a control. You can staple the pieces of colored cellophane to make a sort of tent or hat to cover each pot. Then let them grow for at least a week and see which plants do the best.

Our daughter tried to grow plants under different colors of cellophane, but her experiment didn't give any useful results; because she didn't take care of her plants.

You should do it yourself, and find out! That's what real scientists do!

The main problem with the different color light bulbs is that the colors are dyes that filter out some color of light - you see colors that they don't filter. However, there is more than one kind of filter that produces the same color to your eye. For example, a dye that only removes red light will appear green, just as will a dye that filters everything except green.

Plants use specific colors of light, but you need to know if your light bulb dye filters out some colors or every color. This is going to depend on the dye used to color the light, which will depend on the company that makes the light bulbs.

The idea is right by placing the plant in front of different light sources. But you may have to do it carefully if you want to observe different behaviors when applying different light sources. The truth is that the wavelength of the visible light including red, green and blue are very close. And the light bulbs produce a broad distribution of light wavelengths. That means the difference in those red or green light bulbs is quite small and it will make your experiment much more difficult. The wavelength of ultraviolet and infrared light is quite different from the visible light. By using such light sources, it will be easier for experimental observations on the effects of different artificial light colors on plant photosynthesis.

Questions about experimental design are really fun because there are so many ways to answer them. The basic question that your experiment is testing is “is photosynthesis effected by different types of light?” and you can test this any way you like. It seems like you want to test different wavelengths (colors) in the visible spectrum, and that is completely fine (Hint: there should be a difference in photosynthesis when exposed to different colors of light). If you wanted to, you could also test your hypothesis using other frequencies like ultraviolet and infrared but this may add more variables to your experiment. As a scientist designing an experiment, you want to eliminate as many variables as possible so that you only test the specific question you are curious about. For example: you want to make sure you use the same brand of light bulbs in every experiment (with the same power) so that you know that the only difference between the light bulbs is the color of light emitted. The fewer variables you test, the more confident you can be in your conclusion based off the experiment. I hope these tips help you with your experiment, and I hope you learn a lot about photosynthesis. Thank you for your question!