Mine don't have preference on color, but they prefer ones that serenade them. J/K...

I've found that my female is the picky one of the trio....she tends to have a stronger feeding response only for small white rats...I've put in tan, brown, and black hooded rats and she seemed disinterested, so I always feed her whites.

I'm not sure what it is about color, but for her I guess that's the trick.

Jason