...I would guess it's just lights then. I've got mine 1 or 2 inches below the water surface with my 250w MH DE's.
That's 1 coral that seems like it can't get too much light. I've tried rearranging things before, and it will go pale but once moved back up, it colors up again in a couple of days.

Mitch

I agree. Since I moved the green birdsnest to the top of the tank, it has coloured up a bit already. Going to leave it there for now, but I am installing 400W lights soon. Hopefully I can move it around after that :)