[QUOTE=lilruffian;991034] I believe that certain horses carry the dun gene, grulla gene, red dun, etc... QUOTE]
Just a note there is no "grulla gene", just a dun gene, grullo is black + dun.
I don't know enough about fjords, so no idea how their colors work, I've seen a pic of a grullo fjord, but not a red dun or white dun(?). Because all fjords are dun, you've got that covered. For red dun, the best way would be to breed red dun to red dun, but you also have a chance as long as both parents carry a red gene. For grullo (again, starting w/ two grullo's, and guaranteed if one is homozygous for black would be best), but as long as neither are AA and one or both are black based there's a chance.