Oooh a yellow rat snake! I have one of those. A feisty male. And by feisty I mean he hates, bites, and musks everyone. They do have awesome eyes though - nice, bright and orangey in comparison to the body. I wish mine were nicer.
I rescued him from a lab, where he was supposed to end up as food for a kingsnake. Perhaps he was traumatized! He does have a rather impressive scar on his right side...
Sorry, rambling. As far as breeding goes, you could breed it with a corn, but I don't think hybrids are quite as popular because the color variations are more limited. But if yours is a girl and you want more yellow rats, I'll give you mine!!!