I have noticed that giving more actinic,(o3),blue spectrum helps with color. Also the addition of food (not additives) can help also Iodine to help build Zooxanthellae.
I'm cheeting from Eric Borneman's book"Aquarium Corals"
Yellow-orange carotenoids
pink-orange astaxanthins
pink astaxanthins
orange astacene,xanthophylls
purple astaxanthins