Rat's eyes are quite similar to human eyes -
"Humans have two types of photoreceptors: one type that senses light and dark, called rods, and one that senses colors, called cones. We have three types of cones: green, blue, and red. Rats have rods and cones as well, but only two types of cones: green and blue. Therefore, rats are unable to see reds. In addition, the rat's blue cones are sensitive to shorter wavelenghts than our blue cones, which means that rats can see into the ultraviolet (Jacobs et al. 1991). Behavioral experiments have demonstrated that rats can discriminate between greens, blues and ultraviolets, but also that these colors may not have much intrinsic meaning to them (Jacobs et al. 2001). Rats don't have as many cones as we do -- 5% of the human retina consists of cones (Hecht 1987), compared to 1% of the rat's retina (LaVail 1976), so their perception of color may be much fainter than ours."
Extract from here -http://www.ratbehavior.org/Eyes.htm#RatVsHumanEyes