Just butting my way in here.
Regardless, people would be freaked out by what they see. I think I heard that birds see in ultraviolet. People would think they'd be tripping majorly or something. And they wouldn't be able to talk to ask what's going on. Unless they're a parrot or something similar.
Vision is a pretty crazy topic, and someone can feel free to correct me if I've gotten any of this wrong.
Many animal species can see into higher frequencies than humans - parrots, reptiles, some insects, for example. Whatever they see in the ultraviolet range is probably some "color" so foreign to us that we could never imagine it. However, bees can't see anything in the red frequencies at all, and parrots can apparently only see limited reds.
What frequencies animals can see is different from color differentiation. Even though parrots and bees have a mostly similar range of vision, parrots can recognize a wider variety of colors within their vision range than bees. This is because parrots are Tetrachromatic (4 cones in the eyes), and bees and humans are trichromatic. Parrots can perceive ~100 million unique colors within their visual range, where humans can see about 10 million. Bee cones are different than ours - ours respond to red, green, and blue, while bees' cones respond to UV, blue, and green.
We've pretty much figured out that dogs and most other mammals are Dichromatic. As far as science can tell, dogs are red-green color blind. We think they see everything in shades of yellow and shades of blue-ish (this is a rainbow according to a dog, or a human that's red-green colorblind.) There are only a few monochromats (that we know of) - pinnipeds (seals, walruses, sea lions), and cetaceans (dolphins, porpoises and whales). They may see only in shades of gray....or perhaps only in shades of red, or only in shades of green. *shrugs*
So...think of the ridiculous havoc that would be caused with hundreds of animal-people suddenly trying to drive or something. Everyone would have such wildly varying perceptions of the world, and there would be no way to create a standard system of colors and their meanings because of it.
I'd stay off the road, probably. Forever.