i don't see a problem with dyed foods as long as they are safe, like vegetable dyes (beet juice, blue/green algae), vitamins (beta carotene, Vitamin C) or FDA approved dyes. many animals in the wild get their color from the foods they eat, like flamingos. then again it won't give the an unatural color, just a healthy normal coloration. except maybe for albinos. . .
None of the fish shown look similar to the fish I've seen that were fed dye in their foods. The foods tend to produce a muted color change, nothing like the neon colors shown in those pictures.