Much like leopons have Kimanjano which can be passed, what if certain muties always have a unique mane they are always born with from that mutation which can be passed to cubs? Primal (regular), Felis and Smilus are the most obvious ones but I'm sure many of the other mutations could also have unique manes, such as leopons, dwarves, future tigons, etc. Perhaps polycaudal could have a unique mane that has a slightly split tail tuft on non mutated cubs!
Even existing manes could be used, tsavo (or a similar thin mane) could be the default for maneless, for example.
This would obviously not automatically change previously born cubs, perhaps unless given an option to.
I may add some mock ups in the future, if you have any suggestions or art you'd like me to add, let me know!