Thanks for your question. Dogs are not color blind. But they see  the world quite differently to us. In dogs retinas, they have fewer cones but more rods compared to us. More rods means they can detect movement and light better than human. The cones are responsible for color vision. so that dogs can see color. But they just see it differently.

Dogs vision is dichromatic, so they primarily see blue and yellow color. Humans usually see trichromatically with visible variations of red, blue and yellow color.  So,I think a dog’s vision is similar to being red-green color blind, which is a common variability in us.

Actually, we really don’t know how dogs see. We can just make this assumption based on their retina and it’s cellular level. It is quite possible that they assign colors in a completely different manner to us.  They could rely on brightness and contrast to identify different colors more than what humans do.  For example, a dog can not be able to differentiate a green ball compared to a red ball. But the dogs may be able to detect a difference in the brightness or contrast between two balls.

They are much better than humans in low light situations. They are known as crepuscular hunters. So that they are much better at spotting that possum up the tree in the yard at dusk. This is certainly an advantage for dogs.

Their vision is a little fuzzier than humans. The measure of visual acuity is often stated as a normal of 20/20 vision and it basically means that at 20 feet we can see two things that are 1.75mm apart. They vary in their visual acuity and their Snellen rating can be estimated to be around 20/75. The Snellen rating means that they can recognize lines on a chart at 20 feet and a human could detect that at 75 feet.

So, dogs don’t see colors quite like we do and they have slightly fuzzy vision. I think their eyes are better adapted to movement and low light.