Canine vision is much more complex than we once thought. Not only are dogs able to determine some colors, they have certain eye abilities that surpass our own.
How Your Dog Sees the World
Your dog sees the world from about one to two feet off the ground. Canine vision has evolved to fit their conditions and lifestyle. Typically, dogs judge an object in three different ways. The first is motion, the second is contrast (a dark figure against a white background), and the third is color.
Superior Sense of Motion
A canine's sense of motion is far superior to a human's ability. Perhaps this is one of the reasons why many dogs don't show interest in television, as instead of seeing fluid moving pictures, the dog sees flashes of light. That is, the many individual flashes of a single picture on a film strip that create the fluid motion we perceive. In fact, a dog's determination of motion is so good, it can see a moving object more than half a mile away. However, if that item is stationary, a dog can only determine that an object is there if it's 600 yards away.
Visual Acuity
The average dog has 20/75 vision, meaning a dog sees the same thing at 20 ft. that a human with normal vision can see at 75 ft. Also, objects closer than 33 cm. to their eyes appear blurry to dogs. Compare that to a human with perfect vision who can still see the details of an object only 7 cm. away from their eyes.
Field of Vision Correlates with Nose
The range of vision a dog can see is relevant to the breed and how close together his eyes are. As a rule of thumb, the longer a dog's nose, the greater his field of vision (the more he can see in his peripheral vision). A human's total view is about 180 degrees. A Pug or Pekinese dog has a field of vision that is 220 degrees, while a long-nosed Afghan Hound or Borzoi has a 290 degree field of vision.
Limited Color Perception
Like human eyes, canine eyes consist of cones and rods; however, there is an emphasis on their rods, while we have an emphasis on cones. Their emphasis allows them to see in the dark and dim light four times better than we can. The emphasis on human cones allows us to have a greater spectrum of colors in bright light. We have three cones, while dogs have only two. Contrary to popular belief, they are not color blind, but able to determine various shades of violet, indigo, and blue, and possibly red. They have difficulty distinguishing colors between green, yellow, orange and red. The color blue-green appears white or a shade of gray to them. Though our canine companions seem to have less ability determining colors, they are actually much better at differentiating subtler shades of gray than humans are.