This is because cats have a different type of photoreceptor in their eyes than humans do. Humans have three types of photoreceptors, called cones, which are sensitive to different colors of light. Cats only have two types of cones, which means they can only see a limited range of colors.
In addition to blue and yellow, cats can also see some shades of gray. They can also see ultraviolet light, which is invisible to humans. This is why cats can sometimes see things that we can't.
Here is a table that shows the colors that cats can and cannot see:
Color | Cats can see | Humans can see
---|---|---
Red | No | Yes
Green | No | Yes
Blue | Yes | Yes
Yellow | Yes | Yes
Orange | No | Yes
Purple | No | Yes
Brown | No | Yes
Pink | No | Yes
Gray | Yes | Yes
Ultraviolet light | Yes | No
As you can see, cats can see a limited range of colors compared to humans. However, they are still able to see the world in a rich and vibrant way.