Well I have two birdnests in my tank a green one and a tubs.
The green one has been at 10" in my tank and has been growing crazy. The polyps are very very well extended and I am not loosing color (found that the skeleton of this one is brown).
The tubs birdnest (purple polyp with green body) is around 15" in my tank (height from the bottom). When I had the two T5s; it's skeleton was turning green as it should be but then when I changed it to four T5s, it became brown :S
That obviously made me conclude two things: high nutrient (no) or less light (seriously?!).
So I did some searching and came to find out that green, purple, etc. (other than the pink one) colors up well in low light while the pink one needs high light! WEIRD!
Well that do makes sense since my light increased and the tubs is turning brown.
So hoping someone with tubs birdnest can chime in
