Remember also that many (most?) animals don't have trichromatic vision like we do, and so won't be able to perceive certain colours as 'different'. Dogs can see yellow and blue very well, but red and green look identical - i.e. grey. They're also short-sighted compared to us, and their 3D perception is weaker due to their relatively side-mounted eyes. However, they're much better adapted to low light levels than we are, and can almost see in the dark. I don't know what bird vision is like, but I would imagine it has similar specialisations/limitations.