Birds sometimes are born with what is known as mismatched eyes. One being a coloered eye othere being a different color. . NOW these birds let to breed can send the same over to there young. The birds them self can see just fine. You will also see split eyes where the bird can have two colors in the same eye. Just a wonder of nature.
Odd eyes are pretty common in some breeds/coloration. It seems to be associated with baldhead mostly, just like a lot of your pied birds will have split eyes ('shadows' in a colored eye, sometimes splitting it to half black half colored). Many, many of my baldhead birmingham rollers were odd eyed. They'd have one white (pearl) eye and one black (bull) eye. Makes you think you have two different birds depending on which way they're facing
If the bird has white feathers on the head you could have a bull eye on one side and a colored eye onthe other.Abull eye will look black. mormaly birds white white on the head have two bull eyes ,some birds with a white head will have colored eyes because they have grizzle in their make up GEORGE