I think there has been some discussion about the possibility that gut loading with beta-carotene will enhance the oranges, but I don't remember where (or if) I read that.
Well it's hard to do because every gecko is different obviously, so you'd have a difficult time finding a constant to compare things to. I think if you tried it right for a few seasons, finding food high in beta-carotene to gut load with, and try it out with tangerines or other stable-colored morphs, like normal's even, then you could come to a conclusion. Maybe get a few breeding buddies in on the project, too.
But things like heat, diet, and stress all contribute to color immensely, so thermostats and stable environments would NEED to be put in play.