well, you really need to hook it up with some more info on what your tank setup when you ask a question like this, but I will attempt to help you anyway.
I was at this fish store that had some LPS corals in tanks about 12in deep with a superblue and a GE 6500k starcoat (individual reflectors) above them. I bought a sort of ugly browninsh brain with minimal green in it from them. After about a month in my tank which has 4 T5 and is 18' deep with no 6500k light, the coral colored up to completely green. Even though I had more light in my tank, the increased depth and lack of 6500k spectrum really colored in my coral.
My guess is that you have too much high spectrum light (red, oj, yellow light) or maybe just too much light. However, I think corals can take alot more light in the 20,000k range then they will tolerate in the 6500k range.
but, you still should post what kind of lights you are using and on what depth (inches) you are dealing with.