In short, snakes do see in color. Their eyes contain rods and cones as we do, yet do not have the variety of photoreceptors that we carry, so their color perception is not as expansive. Snakes, being eyelidless, have a filter that works to absorb harmful ultraviolet light as well.
Of course there are snakes that can also see by means of infrared detection. Pit-vipers and some boids are included here.