The silver you describe is a pattern more than a color.  The mixing of the
dark and light guard hairs is not limited to the black and white - we've
got chocolates and cinnamons with the white mixed in.  Some call these
choclate silve rmitts or cinnamon silver mitts.  You did get me right in
that I think - though this is still an opinion - that a typical silver mitt
is a black sable with a pattern overlaid.  The light silver mitts have the
addition of roaning (the mixed light guard hairs) with the mitts.
 
Farrah Shimbo - who has the most detailed book about ferret genetics I've
found yet - even differentiates between the white feet of a mitt and the
white feet os a blaze or panda which she calls socks.
 
There are different opinions from all the breeders I know and it will
probably be quite a while before the real 'truth' is worked out.  One of
my goals as a breeder.
 
bill and diane killian
zen and the art of ferrets
[Posted in FML issue 1210]