This is the photosythetic action spectra

action20spectrum20en - The meaning of Lights?

This is basically shows how effective different wavelengths are at feeding the photosynthetic process. This graph combines chlorophyll A and B. You can find the graphs for each chloropyll online easy enough if you want to break it down further, but this shows what 99% of reefers want to see.

If you want the most ideal light source, recreate this. It's not very practical, and it's not going to look good either. It would be the most efficient use of energy though. The important area that we want to hit is the area between 420nm and 460nm. That's where the bulk of the work is done. The area between 630nm and 680nm is important too, but not quite to the degree that this graph shows. Those are the two peak areas of the visible spectrum where photsynthesis makes the most efficient use of the light.