p l u t o said:
Color changing markings. So only the markings change color, kinda like a chameleon. The more dynamic markings it has, the rarer?

Fin markings. This one is kinda limited to the spieces, but it sounds kinda cool, i dont even know if it has fins but heck it. When the fin is "out", there's no marking. But the fin can change into a marking so it's "hidden". Can also be done with like add ons, for example those angler fish things.

N e m o

Panda like markings?

Markings that get bigger, or smaller depending on age.

Markings that change depending on where you look at them. Now this is a rather complicated idea, so i dont know how it would exactly work oof :'D

Freckles, spots, splotches, etc.