I have heard of "orange bellies" which are apparently a variation of YB. I can't remember if I've ever seen a pic of one, so I'm not sure how brightly colored the bellies are.

I also saw one classified this year for a CH that had a bright red/orange belly.

Another possibility other than the pre-shed color is some sort of burn or scale rot. I get the impression from your other posts that even though you aren't much of a BP person, you have enough experience with snakes in general to recognize something like that, so I'm mainly mentioning it for any one else that might read this thread trying to figure out what is wrong with their BP.

We want pics!