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They are specific wavelengths for plant production (well for optimal growth) but plants generally only absorb the red and blue spectrum of light, the other colors are reflected out and we see the plant as green. So although they sell "full spectrum white grow lights", 50% of the energy used to put out that light is then wasted.

Okay @steempowergarden this is very interesting, I have seen some different experiments with different color spectrums lights on growing plants... It is interesting with uv light also, I wonder about uv-a and uv-b...