I was fortunate to pick up a chocolate Silver Fox rabbit earlier this month. Most Silver Fox rabbits are black with the white hairs mixed in that are called silvering. Currently, only the black color is officially recognized by the American Rabbit Breeders Association but the National Silver Fox Rabbit Club recognizes that five can occur- black, blue, chocolate, lilac and white. White Silver Fox rabbits are considered undesirable, but the other recessive colors are sought after by some breeders. The blue was even recognized by ARBA years ago, but was dropped as there were too few blue Silver Fox rabbits showing at events. Currently, some Silver Fox breeders are working to restore the blue to recognized status and add chocolate as well.
It's really interesting to me to understand the genetics of how this works. A rabbit will be black if it has one copy of the black gene no matter what the other gene calls for. A rabbit needs two chocolate genes to appear chocolate brown rather than black, although a black rabbit can produce a chocolate if the gene for chocolate is present but hidden. Blue is a dilute for black. A rabbit needs two copies of the recessive dilute gene for it it show. Blue is the dilute of black, and lilac is the dilute of chocolate. A black rabbit who also has one chocolate and one dilute gene will be black in color but able to produce any of the four desirable colors. A black rabbit with no genes for chocolate or dilute will never produce anything but black offspring, no matter what color the other parent is.