I do have some Welsh Harlequins I've crossbred with, just for fun :). But I don't breed them pure very often.
Anconas have the black gene (most of them) and some of them can have "rust" or pencilling over it. I'm not sure what gene causes it, but that could be what's going on with yours.
He is beautiful! It looks like a claret breast to me but I don't know whether that's possible on a black duck or not. @Pyxis might know. I've found the genetics can be very surprising in the ways they are expressed sometimes and there is still a ton I have to learn.
I'm also not sure if eye...
The silver phase is snowy; however, since you didn't get bibbed ducks from your Black x Welsh Harlequin crosses, maybe your Harlequin drake has the dusky gene. That dusky gene removes the bib. I did read somewhere that gold phase Harlequins had dusky and silver did not. But I have a silver...
Because the harlequin gene is recessive, it could be carried without showing in the first generation of mixed ducklings, but then show up in their offspring and look like pure Welsh Harlequin. The black gene is dominant but since the black ducks would only pass one of that gene on and the...