Then I think they should be off-white... ...you could use the Pokedex entry to explain, of course... ...but, I think at this point the connection between picture and Ghost/Fighting needs to be intuitive.That axe is bone, though. His other forearm bone.
I tried to make it pretty obvious that my last one was a Fighting type (great big fuck-off boxing gloves and a sturdy physique) but I guess when you're drawing you just can't win, so I know how it feels. Still, off-white would look cool and more original than that silvery-steel colour.