I find New Life Spectrum to be fairly lousy in terms of enhancing colour. It seems to be a great food in quality and ingredients, and my African Cichlids look great and are in fantastic health since I switched them to it as their primary diet. However, they have since lost the intensity that they had before.
I would really like to try Dainichi foods. I might order some and see about selling at the store.
As far as the food with the most effect of colour enhancing, I would say Tetra Colourbits. It's changed names not too long ago, and now just reads "TetraColour: Tropical Granuals", but it's made by Tetra, in a yellow bottle, with red cap. This stuff may not have all the great whole and natural ingredients, but it must be packed full of Beta Carotene.