Yup, my gibbiceps have lovely orange/red highlights on them. There was a time that i fed one with and one without, and the one grew to have a lot more red pigment, but it was hardly a conclusive study, as every ones an individual. However like COL said, chances are it will make them more colourful, and i suppose more specacular effects would be created to fish that already have the red pigments on some level.