As Cecil Adams observes in The Straight Dope cats and dogs are not completely colorblind but one can compare their vision with the vision of human being suffering from Deuteranope. The same is reported from Earth & Sky and as I read through my conclusion is: They are just not interested in colors. In their lifes there are much more important things to do then to distinguish different shades of color. Maybe it’s the same for us colorblind: Just more important things to do than spotting red flowers in a green field or learning that the sky is blue even if it is gray all day long these days. I would say we can concentrate much better on our work and don’t get abstracted by seeing our world full of colors. We get the work done!