Green Fluorescent Protein (GFP) has intrinsic fluorescence, built-in to its structure. It does not need to be within a chromatophore to fluoresce.
This is why it is useful to so many biologists....if you want to follow the movement or development or development of pretty much any tissue, you can try to selectively express a GFP protein in those cells and then you can shin UV light on the organism and watch for sometime to gather the data you need.
If you want to track a particular protein, you can try to fuse the protein with GFP to track the life of the protein in an individual cell.
Basically GFP has been shown to express itself and function in all kinds of cells.
Wild-type GFP fluoresces green, but researchers have created mutant GFP proteins that fluoresce different colors. http://en.wikipedia.org/wiki/Green_f...FP_derivatives
Maybe a Leucistic ball python might show the fluorescence better than a wild-type because there no other pigments to interfere with it.