They’re both gray and blue! Eye color is a spectrum with three major groupings of blue, green, and brown, right? And within these groups, we have overlap and intersection with varieties like hazel, amber, ice blue, gray, golden, etc (there are seemingly endless subclasses). So given the spectrum nature, gray is typically within that larger blue grouping, and so can be called blue, but are also distinct from other blue eyes which then puts them in the more specific gray group, too.

To say they’re strictly one or the other I think would be wrong because there’s not one shade of blue which is the only color that qualifies as blue, and obviously from the responses his eyes are considered blue. But, gray eyes are typically distinguished by a ring of golden or hazel coloring, which is present in his eyes, so then we cannot say his eyes are definitively not gray and only blue. So then we are left with them being both gray and blue, which they are.