Just read an interesting article:
http://www.coralscience.org/main/art...-5/amino-acids
According to the above mentioned article amino acids do indeed help the growth of coral, especially in nutrient poor systems. In the wild about 20% of a corals intake is amino acids, however in our home aquariums we can "trick" the coral into using quite a bit more. My conclusions based on this article is that amino acid supplementation may be necessary in situations where your coral are looking washed out due to a lack a nutrients.
So thats amino acids...now how about other supplements to help with color?