Second, lighting, red LED lights are necessary. There are many types, basically divided into two categories, a class of fish red water red, a class of fish red water is not red. Depends on your personal favorite.
Third, the environment, dark environment is conducive to fish color. For parrots, black bottom sand, black or blue wallpaper, are conducive to increasing red.
In fact, the most important thing is the fish species, the fish is not good, the above measures, can only be slightly improved.
The rest is a matter of personal nutrition (others have answered you), which has nothing to do with the hair color, but is related to the health of the fish. Unhealthy fish don't have perfect hair color.