I'm assuming you mean just "Silver Marten"because there is no such color as an Black Otter Silver Marten (not possible - has to be one or the other).
Tan at the nape of the neck would be an otter, white at the nape of the neck would be silver marten. Photos would really help, so we can be certain of their color.
The most likely color you'll get is Chinchilla.Silver Marten is the second most likely color (It depends on what the Chin is carrying in the "A" series. The Chin's "A"agouti gene is dominant over the Silver Martens "At" tan pattern gene).
Many other colors may also be possible (including albino, smoke pearl marten, sable marten, sable, sable point) depending on what recessive genes the pair may be carrying.
You can rule out any full "C" colors such as tortoise, chestnut agouti,lynx, opal, otter, fawn or orange because neither of your rabbits carries the genes to produce those varieties.
Personally, I would not risk the doe's health by mating her if you are not breeding for a particular purpose.
Pam