Ed, I have wondered. Do you think both UVB exposure and caratenoid supplementation is the way to go with the deep red tricolors? I know you said it stimulates melanophores, but I have theorized the "rich red" types could be simply from enough UVB exposure.
What I'm saying is, that the frogs while tadpoles should be given mostly caratenoids, and only as adults or subadults be given UVB. I make this hypothesis based that young tricolors are mostly shy and blend in well in the substrate while the adults (particularly the males) become much bolder and often climb upwards...in nature I think as adults they would be more out in sunlight than the youngsters.
Here's something interesting, but there is no true evidence. The two male tricolors are definitely deeper in color than the female. They are more brown, but it definitely looks brick red, very nice actually. The female which is virtually always in the shadows is mostly that "bubblegum" color which is pretty distinct. The males stay up near the plants where they are exposed to more UVB from the light.