Although it was previously believed that dogs could only see in black and white, new studies indicate that dogs have limited color vision and can see the colors blue, yellow and gray. Dog do not have the ability to see the range of colors between green and red.
The reason for a dog's limited color vision is that its eyes only have about 20 percent of cone photoreceptor cells. These cells are necessary for the perception of color.
Although dogs may not see all colors, they can distinguish motion at long distances and have twilight vision (vision in reduced illumination) that is superior to humans. These vision sensitivities make dogs good hunters.