And what lighting was it under when you bought it. Might be more lighting than it was used to and is having a zooanthellae bloom (symbiotic algae) and will regain it's color when settled in. Here are some things that are good to know when keeping corals and invertebrates.
Alkalinity as in DKh
Calcium
Magnesium
Ph
Salinity as in Sg
temperature
Some others that can help diagnosis such as phosphates, age and type of bulbs, water flow, quantity of live rock, type filtration, water change frequency.