I've heard powdered chlorella works on blue colors, but haven't read any logical explanations why it should. I don't think the blue frogs tend to fade with age like some of the yellows and oranges are said to do. My blue auratus remain their original lovely blue. They also get some of the paprika dust because I dust all the flies I feed to all the frogs at the same time and paprika is a very safe source of vitamin A. (Excess carotene is not all turned into vitamin A-- only what is needed, whereas the straight vitamin A supplement is stored in liver and fat, can't be excreted, and can be overdosed.)
It's actually only subjective, but I do believe the paprika does work on the yellow and orange colorations, and there's a physiologically sound explanation for this as excess carotenes are stored in the lipids of the skin cells.
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Patty
Pahsimeroi, Idaho
4 D. auratus blue
3 D. galactonotus pumpkin orange splash back
5 D. imitator
4 D. leukomelas
4 D. pumilio Bastimentos
4 D. fantasticus pending