Dark/light colours will probably have a dominance/submissive colour effect. Medium tones like this will just blend; markings will blend in the same fashion, so....

essentially, breeding these two cats, you'd get the below. Logically. Obviously it wouldn't be dead ON 50/50. Whatever system devised will have a bit of random chance. Too much predictability is a bad thing, in my books.

Otherwise, more silly concept things. Hopefully this idea will bear fruit. If so, expect more of me blathering on.
...hopefully about something other than cat breeding, and hopefully with some actual 3d models instead of 5 second doodles I decided to actually shade and play with patterns on for some reason.