There are some good sites that have genetic information.
If you want self. Chocolate and lilac are both brown based, chocolate is the Dense color and lilac is the dilute version of chocolate.
aa bb C_D_ for chocolate and
aa bb C_ dd for lilac
If the chocolate carries the"d" dilute gene,then half the kits will be lilac, otherwise they will all be chocolate.
aa B_ C_ D_ is black and if the black carries "b" brown and "d"dilute, you could breed to the lilac and get all 3 self colors, black, blue, chocolate and lilac.
That would make your litters "exciting" in my opinion
I love the brown gene colors. Of course my FAVORITE is AMBER, but that's an agouti color and not recognized in the mini rex.But it is in the standard & I love those litters. Here's one with a black, a chocolate, 2 broken ambers and a broken chocolate.
Like Shy says,the selfs to the otters are OK. I loved some of my broken otters Rex.They are gorgeous.