Dogs can also see many rich colors, but they cannot distinguish as many colors as humans. Because the human eye has 3 types of cones and can perceive 3 colors, but dogs only have 2 types of cones, and the number is not as large as that of humans. Therefore, the colors they see are not as rich as humans, so dogs are red. Deuteranopia.

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Dogs can see blue, but purple also looks blue in their eyes, while red looks earthy, and blue-green looks blue to them. But it looks grayish-yellow, so it’s difficult for us to see their world from a dog’s perspective. At the same time, all dogs are also "myopic" and see many things blurry. If humans can see images 20 meters away, then dogs can only see about 6 meters away.