Kevin, brain corals (both trachyphyllia geoffroyi and trachyphyllia radiata) love to be fed. I feed each of mine roughly 6 large mysis once per week.
Also, gradually working them up to higher lighting typically brings out the colors...and sometimes even more colors.
In my tank, they are placed in lower light areas just because of the balance I'm going for in my tank. With weekly feedings, they have kept their rainbow grade colors even with the lack of light.