I'd think going with matted aluminum fenders would work better. Black fenders would give the bike a bit too much black happening for a classic.
I like black or any color that does not demand the eye's attention...
I did, for a long time, think that color would add to a bike. These days, I try to ensure that the first thing the eye sees is the bike, not the bright cable casing, or bar tape, or saddle, or even bright fenders. Put another way, I don't think the red fenders work on the bike any better than red tires worked on my
Cyclops...
For me, I much prefer the Cyclops these days...
Of course, each to his own and bright colors are safer, adding to one's visibility.