One of them.
If I've read correctly, Cal patterns aren't simple dominant/recessive genes. In other words, you will likely get a variety of patterns 'in between' the two you are breeding, not just one or the other. If you breed a 50/50 to a banded snake that is more black than white, you should get mostly banded snakes that vary between the 2 parents.
The only simple recessive gene I know of is the albino gene. There is an outside shot that both parents are het for albino, in which case 25% of the babies would be albino. You won't know that until you breed them though.