Cats do see in colour but as, Wolflady points out, not as we do. Feline eyesight is very sensitive to movement, but not detail. Felines have very blurry "general" vision and that can only focus well on one thing at a time, it would be like us scanning the distance but only being able to see a small part of the view in detail by using binoculars.

Perhaps this explains why the most realistic looking toy mouse that lies motionless is ignored while a piece of string is considered a prime target...