White-eyed Vireo is a first winter bird, based on the DARK iris. (Red Rocks, Jefferson County).

[Joe Roller]

I had the pleasure of studying the excellent photos others took. (Thanks, Steve Rash).

The lores are bright yellow. 

There is a black line parallel and just below the lores.

The rest of the "spectacles" (partial eye-ring) are lighter yellow than the lores.

But this individual is not "white-eyed", as the IRIS is DARK, a feature of 1st winter individuals. (Sibley)

This individual is of the White-eyed Vireo species, but will not have a WHITE EYE (iris) until it matures.

Which other Colorado (or ABA) species show a white iris?

Joe Roller, Denver