Figure 1 shows the response of chlorophyll a and chlorophyll b to the visible light spectrum. In extrapolating the information in this graph we should provide plants with light that emanates predominantly in the blue and red wavelengths of visible light. Even so, in my preliminary experiment I decide to broaden the spectrum slightly by adding a two more colors of light to the blue and red, namely, yellow and green. My reasoning for adding the other frequencies of light is that photosynthesis may operate more efficiently with a broader spectrum.
* Note: While this experiment did not show this to be the case, I would still leave this option open when growing food stuffs, such as potatoes and wheat. The plants grown under a battery of mono-chromatic light sources need to be checked (analyze) to insure the plants produce a proper (normal) carbohydrate and protein profiles when compared to growth under broad spectrum lighting.
Among all the plant and algae being considered by NASA for long term space flight, the three plants I will probably test in the future are potatoes, tomatoes and wheat. Potatoes have already been to space. According to the published reports the potato plants grew well under the micro-gravity environment.