Totally un-important question about duck coloring/heritage

[Maddog_photog]

Not important question - curiosity is the motivator here: my Swedish Blue ducks have some green that comes out in sunlight in the feathers on their head. Does this imply some Cayuga in their family history..? Or do all ducks with dark feathers have this very beautiful coloration?

 

[FuzzyCritters]

A lot of black ducks have a green sheen. It doesn't mean cayuga.