Black is not a recognized color to show In Swedish.  You can show the color, but it won't be eligible for the higher prizes.  So it doesn't mean you can't take him to a show, but it means he can't win any of the bigger prizes like best in show or best waterfowl.  I am just assuming you are in the USA, as I don't see any location listed that is otherwise.  Other countries might have a different standard.
The blacks are used in Blue Swedish breeding programs since you need the black in order to get the blue color.  If you want to use him in a breeding program, you will want a clear bib and 2-3 white feathers on the tips of his wings.  They should have a meaty body, but no keel. Although I've never seen a Swedish with a keel. Even breeds that are supposed to have them, often don't.  Think healthy looking moderation. Medium sized duck, everything about it medium.
The blue feathers are supposed to be laced in blue, so feathers are supposed to be laced, but I don't know how you'd know if a black feather was laced in black.