The other colors are needed not just for asthetics. To borrow from the internet:

Important
Definitions as it applies PAR in plants and zooanthellic algae: See the
graph to the left as it corresponds to each of these definitions.

*A:
Phototropic response; having a tendency to move in response to light.
Basically this is the Chlorophyll containing plant or algae "moving" to respond
to a positive light source to begin the process of photosynthesis (initial
growth of plants, zooxanthellae, etc.). This is found in the 420-500nm "blue"
spectrum.

*B: Photosynthetic response; the process which begins
when energy from light is absorbed by proteins called photosynthetic reaction
centers that contain chlorophylls.

*C: Chlorophyll synthesis is
the chemical reactions and pathways by the plant hormone cytokinin soon after
exposure to the correct Nanometers wave length (about 670 NM) of light resulting
in the formation of chlorophyll, resulting in continued growth of a plant,
algae, zooxanthellae and the ability to "feed" & propagate, and without this
aspect PAR (670 NM light energy), zooxanthellae and plants cannot properly
"feed" propagate. The results of the lack of this high PAR "spike" would be
stunted freshwater plant growth, and eventually poor coral health in reef tanks.
This lack of near-red light over 630nm is common to many so-called aquarium
lights.