If you're talking about a Canadian C7 or C8 then the answer is black. Age/exposure to the elements, has done some strange things to some of the finishes but they all started out as black.
If you're talking about a Colt A1 upper with "Brunton Bump", commonly referred to as a C7 upper, then either would be correct.
DK marked uppers have nothing to do with Diemaco. Diemaco has always used the stylized D.