Interesting, I don't think any of my BPs have color preference. I'll be paying more attention to find out. I know that my Pastel doesn't care, she'll eat anything without thinking twice. Absolutely no patience when it comes to feeding day. The prey is in there for half a second and she'll already have it pinned and ready.
My Fire has been off feed for about two months now, she's close to the 1000g wall, though. I do know that the last rat she took was a dark brown one, however that was after she shed too, so I still don't think color matters to her, but I'll definately try a darker one next time just to see.