Cats are color-blind, experiencing a color blindness similar to what some humans have. Most colors are distinguishable, but distinguishing red and green is difficult due to a lack of specific cone photoreceptors in their eyes.
Color blindness does not affect cats, because color perception is not an important aspect of their vision. A combination of all their senses determines how cats interact with the world. Cats' eyes have evolved over time to provide excellent nocturnal vision, which allows them to hunt at night more efficiently. They are able to see well with only a fraction of the light that humans need.