Nothing has been recorded of that. Only spilo and reds have bred in the home aquarium. People have tried to breed cariba but have not had success with fry. Other public aquariums have had rhom spawnings.
Yes, they have been bred for a little while now. Also nattereri yellow form (ternetzi) has also, I believe that's in the same thread? Might not be. Anyways, I've never heard of different Pygo species interbreeding, I have a feeling that doesn't happen. Nattereri and ternetzi probably could/will, seeing as they are the same species.
I have a feeling it wouldn't be all that impressive. Like I said they are the same species, only with some minor differences (color being the most obvious). What color would they be? you wonder. I believe that it will be like in humans, one color will be more dominant and the offspring will be have a greater chance of having that. Think of it as if a blonde and a brunette had children, darker hair is more dominant so chances are the child will have brown hair. Of course there are times when blonde will appear, but things are rarely 100% certain.