l have noticed brighter more intense colors on my fishes with lights on for extended amout of times.
Try food that contains spirulina to help bring out blues and greens, while food with carotene such as shrimps, krills, etc will help bring out yellow/orange/red colors.
Omega One Color food and Hikaris is are good brands, l have used it myself with good results. Alot of people swear by New Life Spectrum though l have never used it myself due to it;s cost.