A science fair participant in Selah, Washington investigated different colored lights on radish in 2000. She set up a strictly controlled experiment, and exposed radish plants to different colored lights, along with clear (or white) light. She did this from seed to full growth. She discovered that radishes grow best in clear light. The slowest growth rate occurred with green light, followed by blue, red and yellow. A commercial greenhouse grower can use this information wisely. The lesson learned is to avoid green colored shade cloth, but rather use white translucent shade cloth for maximum growth.
California State Science Fair participant Allison A. Lopez ran her science fair project on the effects of colored lights on beans in 2002. She discovered that beans grow best when the pots were covered with yellow translucent plastic, followed by green, orange and blue. Plants covered with red plastic did not do well. These findings are also significant. Notice that radishes had slow growth in yellow light, but beans grew fast in yellow. This points to different species of plants responding better to different colors.
Science fair investigator Leah Schoelles ran some interesting, very detailed experiments with Lima beans in 2002. She discovered that Lima beans grow best in natural sunlight. A significant finding was the beans did poorly in grow lights. These lights are designed, theoretically, to grow plants better than sunlight. Her findings revealed the opposite effect on Lima beans.
All the experiments have some common themes. The same kind of plant is subjected to different colored lights, and the growth rate is measured in each color. An experiment like this can be duplicated. Its important to use the same kinds of plants for each group. For example you could experiment with five lettuce plants, five tomato plants and five cucumber plants. Start them all from seed, and expose each plant to a different colored light. Record your findings, and in the interest of the public good, make your findings public.