I make my own gelfood, and add certain things as color enhancer - spirulina is one of them, so is red pepper. It does bring out the red more, unfortunately, it turns the white into a more peach or light red coloration, and it takes a month or two to get rid of that again.
For show fish I have been told by a friend, that prospective show fish are fed color enhancer up to 6 months before a show, but then stopped on that food 2 months before the show, to bring back the bright white coloration. You dont want some dirty looking white on a fish going to a show....!