User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-203.59.104.107-20120718031524/@comment-4212769-20120718090715

Again we are at Black Diablos... The color of her skin changes with the hormones in the mating season.

My theory was a combination of mating season and fertility. In short: While fertile and normal circumstances and after getting babies the hormones are at a normal production for this species making them green/red. When in mating season the hormones increase changing the color to pink/azure (when Diablos can why nor Raths?). And when infertile the color gets gold/silver because of the lack of hormones that don't get produced anymore.