Gray-ish blue

Yes, the pupil can take on a lighter shade of gray, even to the point of appearing shiny and silvery. Red eye is caused by light shining back from the retina in the eye, so with black & white, a lighter shade of gray is the result.

incomplete dominance

I really don't think there is a rare color for Siberians, they can have red/white, black/white, gray/white, brownish/white or pure white coats. Same with eye color they could have many colors or one of each or one eye with two colors.

White. An orca whale's stomach is white, just like that big white patch, which is commonly mistaken for it's eye.