I saw a documentary long ago (not sure on which channel, think on Discovery?) and I found out that they see red as grey, they can see clearly yellow and green (that's why my cats are fans of Brasil football team , they always play on the tv screen when there is some of green and yellow). I forgot about blue, but I think you're right, they can see blue too. Also, they see better in less light, so during the day they see blurry.