Contrary to the popular belief that dogs only see their world in black, white, and various shades of gray, they can, in fact, see some colors.

Wonder why?  Wonder what those colors are?

Both dogs and people can see because of two kinds of cells in the retina of their eyes: rods and cones. Rods are responsible for detecting light levels and motion whereas cones help differentiate colors.  Our eyes have three different types of cones, enabling us to identify combinations of red, blue, and green.  Dogs, on the other hand, have only two types of cones, permitting them to identify the colors blue and yellow.  This limited color perception is known as dichromatic vision.  Dogs are, therefore, considered to be red-green color blind.

While we may have more cones, allowing us to see, e.g., all the colors of the rainbow in their brightest form, dogs have more rods, which help them see objects better in low light or identify moving objects at a faster pace than we can.  This is the reason your own cherished canine companion may be distracted by a bird flying 40 yards away that you didn’t even notice or the reason he may bark at a small animal at night that you, yourself, can’t see.

Because dogs have fewer cones in their eyes, when it comes to distinguishing color, they can’t see the same spectrum of color that we can or see them as brightly as we can see them.  When a person is red-green color blind, it precisely means that: they’re unable to distinguish the difference between those two colors, but they can still see yellow and blue. The same holds true for dogs.  Red, for example, appears as a dark, brownish gray or even black while subtle shades of yellow, orange, and green may all appear yellowish to him.

Since the colors that stand out most for a dog are yellow and blue (purple also looks blue to him), is it any wonder that yellow tennis balls, blue toys, and purple Frisbee's rule? Your own dog may find it impossible to tell the difference between a red or green ball on the green grass since they all look the same to him: slightly muddy.  He will, however, be able to discern any blue or yellow one over the rest, which makes playtime so much more pleasurable – for both of you.

And so, whether you’re engaging with your dog indoors or out, make certain to choose toys in the colors he sees best: blue, yellow, and/or purple.