Does PH effect color?

I have blue/black shrimp that have not really had much color in my tank with sand substrate. I thought it was due to the light color of the sand. I have had them for several months and they are reproducing happily however I have recently added coral pieces in with my filter media to raise the PH, and I am starting to notice some beautiful black shrimp and some that are more blue! (quite a few are still pale in color) :huh:
I added the coral due to the fact that my PH was 6.0 and was effecting my snails shells. Is it possible that with the higher PH they are able to acheive their true colors, or does this simply indicate that they are happy and healthy? (PH is now 6.6)

Thanks pik! I wonder if I should raise it a little more?

I am not crazy about the idea of messing with my PH and would never do so w/ chemicals but with it being so low and affecting my snails I had to do something. I am hoping that the coral will keep it at a steady level...I could put a little more in the filter to raise it upa bit more, but I think I will wait a few days and see how things go before I mess with it anymore......