I know this is old hat to some of you - but I was curious as to cone/rod distribution in herps' eyes and in the lull that followed that query I did a little poking around:

Snakes have rods and cones in their eyes, as do we, though in different numbers. They do not have the diversity colored oil droplets (presumed to have been lost when snakes when nocturnal and subterranean) in their photoreceptors that mammals and birds do, so, while they do have color vision, it isn't as broad ranged as ours is. They do have a yellow filter which, filling the lens, absorbs ultraviolet light, protecting the eye.

Snakes use a combination of infrared vision (developed in the trigeminal nerve), variable (by species) visual acuity and color detection, limited eye mobility, and chemosensation to find prey and recognize features in their environment (including their keepers).
http://www.anapsid.org/sight.html

Interesting site overall to say the least.