From your description, my best guess would be Agouti....this is the coloring of wild brown rats, and breeders have now developed it into different colors as well.
What Agouti means, is that there are multiple colors to each hair shaft....a single hair will start white, go to red, and end in black. That gives a sort of ticked, patchy look.
If you have a picture of her you should post it so we can see exactly what Karma looks like, she sounds beautiful!
