I'm a fan of the hypothetical/undiscovered genes. I'm sure there a few pigment-altering genes (and pattern!) than are currently known.
Ppl have said if breeding a pair that don't show yellow, is no guarantee the babies will be like that.
Has anyone seen morphs other than the 'darker morphs' (~ homo for anery, charcoal, cinder, etc) that lack yellow as adults? If no, it could be tied to only geness that dont eliminate melanin. If yes, that throws out my guess lol.
I'm personally waiting for a tiger stripe pattern, super melanistic, and couple scale structure traits (rough-scale and clear).
DYK we only have a couple decades before genetically altered reptiles show up. It will all hit the fan then.