I had a mature ocellaris and added a black ocellaris, they are inseparable and have been spawning for 6 months now. I should try to raise some eggs to see what they look like.
From my experience, you need to match aggression levels closer than exact species. My black ocellaris is twice as aggressive as my orange one, but my orange one (female) is twice his size, so everything is gravy.
Clownfish will hybridize with completely different clown species, you just need to make a wise choice when it comes to age and aggression of your new additions.