Cats have color vision, and can even see ultraviolet, but the range of colors they can see is different from and more limited than what most humans see. There are two different kinds of cells in mammalian eyes, and cats have more of the kind that pick up dimmer light.
These cells, called rods, are excellent in poor light conditions, but they are better at picking up contrast than at perceiving color or fine details. The cells in the eye that are responsible for color perception are called cones. Humans who are not colorblind can distinguish blue, green and red clearly, as they have cones for those specific colors. Cats mostly see in shades of blue, violet and yellow, with a bit of green. They can also distinguish ultraviolet, which is useful when hunting animals that are well-camouflaged in the visual spectrum. Urine especially reflects ultraviolet, allowing cats to both see and smell territorial markers.