I often notice this effect when lying in bed with one eye open, and the other closed on the pillow.
The closed eye will be bluer, the open redder. My own theory (backed up by nothing but a hunch) is that the closed eye adjusts its white-balance to compensate for the red light coming through the eyelid by becoming bluer.
This. You can try it on a bright day easily by alternating your open eye, and closing both with hands over them for a while to reset the phenomena. I discovered it decades ago on an extremely bright day where I couldn't keep both eyes open without discomfort.
The closed eye will be bluer, the open redder. My own theory (backed up by nothing but a hunch) is that the closed eye adjusts its white-balance to compensate for the red light coming through the eyelid by becoming bluer.