Light emitting diodes normally emit monochromatic light according to its color.
There is red, green, yellow and blue. One can synthesize white light by mixing the three colors RGB. The plants need light of specific wavelengths to for its photoelectrochemical activities and growth. One has to see what is the absorption band of a specific plant and supply it with such source of light. I do notnt know how the plant behave with the light intensity. I mean if its behavior is linear or nonlinear in the sense as one increases the intensity of light with the suitable wavelength the production of the energy increases and the plant can grow in higher speed up to certain light intensity after which the plant can suffer and its growth rate can be decreases again. I mean, they may be an optimum intensity of light for the plant.
There many scientists on the RG who did intensive research on the effect of LED lights on the growth process of specific plants.