Very good question. I wonder that too. I have a YB pair, and my male is not awesome in the blushing/flames dept., but the female is. And she has an orange tint to her belly. I didn't think I'd be able to breed her this year, but she's gone back up to 1300 grams in a few weeks of consistent feedings, so we'll see what she's at in late December/early January.

I gotta say, though, I'd be happy with a dirty Ivory, clean Ivory, etc. for the first year.