I'm trying to understand more about breeding deviants, I think I might understand now and was hoping for conformation. To breed a deviant you have to have a double homoginous such as 

gray/gray

cream/cream

When breeding the pet does it have to be bred to another pet with the same variation of homoginous or can it be 

bay/bay

striped/striped

I'm just trying to understand more for developing my program.

Ok, for deviants:

Mother has to be grey/grey, father has to be grey/grey etc.

(Child will hopefully be grey*/grey*)

For double deviants:

Father has to be grey*/grey* and normal/normal

Mother has to be grey/grey and normal*/normal*

Child will hopefully be grey*/grey* and normal*/normal*

I think I get it! So it has to be the same formula and not separate. That does make sense.

Anytime you have a creature that will end up with homogynous color or pattern there is a 10% chance it will become a deviant.  This is easier to do if you have two homogynous parents, but if you had a gray/white and a gray/black and the baby inherited both the grays it also has a chance of being a deviant.

This is true. I've gotten like two "accidental" dviants this way. The chance to get a deviant is 10 per cent even if the parents are homozygous.