* Colors Dogs Can See

Colors Dogs Can See

The reason dogs can only see certain colors is because of the photoreceptors in their eyes. Both dogs and humans have rods and cones in their eyes, but humans have more cones, while dogs have more rods. Also, humans have three types of cones, but dogs only have two types.
Ref:  http://starlocke.com/dogvision.htm

 but, i m thinking about  how they know dog was seeing like that?  :-)