Chances are pretty good that if a magic horse teleported you into the middle of any cluster of cars in America, parked or in traffic, you'd find yourself surrounded by grey, white, black, and beige-ish cars. Don't blame the horse — the sad truth is car colors are pretty damn dull. What colors should be used more?
As it stands right now, only the extremes of the market — the extreme low or high ends — actually have vivid, interesting colors. I suspect there's a certain confidence and willingness to have fun when you have either so much or so little money, you just don't give a shit what people think.
Personally, I'm a huge fan of yellow, but there's plenty of other colors that cars look great in, like vivid lime green, or orange, or maybe whatever blue that traditional French racing blue is.