I'll put in my two cents. One of the main things I look for is, do you see one eye or two. If you see just one eye most of the time its probably a deer. With most predators you will see both eyes. You will many times be able to make out their gait. I also try to determine how high the eyes are off the ground.
As far as color of eyes go, under a white light, I've seen deer eyes that were blue, orange, yellow, white, and just about every thing in between. Racoon eyes mostly have a orange cast and so do grey fox. Bob cats have a green tint. But under a red lense they all look red.