These images are of 3 sibling captive bred blue jeans showing variation in color.  These pictures were all taken from within the same vivarium and same lighting.  The colors are pretty representative of how they look in life.   The frog in the middle was reared inside the large natal vivarium and fed largely on the small arthropods that live naturally in the vivarium leaf litter.  The other two frogs were pulled at a fairly young age from the vivarium and reared on dusted fruit flies.  Notice the red dot along the lower left dorso-lateral line on the frog on the left.  That is actually a few granules of skin that are pigmented bright red.   This lends evidence that the differences in color are environmental rather than genetic.

I suspect there is a fairly narrow window of time when a frog's colors are "set" and I believe this window is from  late tadpole to a few weeks after morphing.  Over the last few years I have been experimenting with canthoxanthin as a coloring agent.  Canthoxanthin is a potent form of vitamin A and can cause liver damage so I have mixed a very small amount into a jar of vitamin dust and have been dusting once a week to once every two weeks with the mix.  All of the frogs above received that treatment to various amounts. 

The traditional way to color up red frogs is to supplement with beta-carotene which is a safe pre-vitamin A compound frequently found in amphibian skin chromatophores. From discussions on PDF forums and literature reviews of amphibian pigmentation, I believe difficulties with coloring red frogs may be due more to a lack of variety of carotenoid pigments rather than the quantity of one carotenoid.  Recently I have created a carotenoid rich dusting powder derived from dehydrated fruits and vegetables. The ingredients were chosen to represent the best sources of the major caratenoid groups (http://food.naturalhealthperspective.com/carotenes.html).   Lycopene in particular seems promising as a coloring agent.  It is the pigment that gives red tomatoes their color and it has low vitamin A activity so should be very safe to use.  Like all carotenoids, lycopene is stored in the fat so it seems likely that animals fed these carotenoids as tadpoles or young froglets may store these compounds for use in developing chromatophores later in development. 

In addition to dusting fruit flies directly, I am also using the dehydrated fruit and vegetable powder to supplement feeder insect diets hoping that some of the carotenoids will accumulate in the insect fat.  After just two weeks after sprinkling the powder in a springtail culture, about half of the springtails look noticeably more yellow than the others.  I have also sprinkled some of the powder directly into the leaf litter of the large natal pumilio vivarium hoping the carotenoids will be consumed by the small vivarium arthropods.  Only time will tell if this experiment will be successful or if it can enhance the coloration of already mature frogs.