Comb is usually much easier to fix than color, as long as you still have the correct comb type in the breed to work with. If you have to cross outside the breed to bring in the new (correct) comb type then obviously that is very tough to fix. Of course this depends upon if you are fixing and existing comb type or if you have the wrong come type all together and even then it depends upon whether the correct comb is dominant or recessive etc.
Well, in this case it is recessive, of course, I don't know if it matters too much until you finish getting them there. I just really like black birds, and the shubert blacks are basically a melanized red duckwing from what I experience. They are definitely not E based. So I figured, might as well make a black longtail that isn't a sumatra.. lol