I got my first pearl the other night, and was disappointed that it wasn’t additive to my normal skins. I used to breed snakes, and I think you could add some gameplay to genetics this way.
A creature would have a natural pattern to their scales. Morphs would add to or take away from those patterns allowing you to have a much wider array of possible skin outcomes. In addition, the morphs are different alleles so it’s possible to pass more than one trait on. Pattern morphs and color morphs could be used. Recessive and co-dominant traits.
A snow boa is a combination of an albino and anerythristic which basically removes the blacks and reds. As a young snake they look white, but they yellow up as they age.
A simpler approach would be to just have things like pearls be additive. A melanistic dragon with a given skin would look different, than a leucistic with the same skin.