Ducks With Grey Eyes

[Wild-Turkey]

Hello,
I have a very mixed flock of 16 ducks, four are drakes. Seven members of the flock are Black Swedish mixes. One of them inherited his father's unusual trait, grey eyes. I could not find anything about this or any other ducks with this. I was wondering if this is a mutation or the result of an inheritable disease or infection? Neither of these boys, or any of the other offspring have exhibited any symptoms of an underlying condition. I'm curious if this would be safe to breed into more ducks. Hopper, the larger, smooth-bibbed drake, also "quacking" in the picture below, is a Pekin and Black Swedish mix, Mister, the leaner, broken-bibbed drake, preening in the picture below. Both have been extremely healthy, no issues or defects.
Thank you

 

[Isaac 0]

I would suspect some weird genetic mutation if you saw the same ocular coloration in his father. As long as the duck appears to be healthy, and you're fine with such a trait, I would see no reason why it wouldn't be safe to breed offspring using him.