General Discussion

Reason 1: the two cheapest colors of car paint are black and white, and by extension silver and gray. Black, because it uses carbon black as its pigment, is the cheapest of all. Unlike house paint, where all colors are the same price, different colors of car paint have different prices. It's all in how much the pigments cost: darker pigments require more processing and more ingredients to make them UV-stable.

Reason 2: the least expensive paint to apply is white because it doesn't show flaws. Light colors like silver and gray are similar. Black is REALLY hard to get to look right because it shows everything, but the price of the paint is low enough to make up for it.

Reason 3: people are afraid of color. As a graphics professional I've known this for decades. They are scared as hell of color, especially bold color. The psychology is people are scared of other people thinking negatively about them if they use color, so they go with the flow and don't use it. People paint their homes bland colors, both inside and out. They wear clothes in muted colors. They wear simple jewelry that's just silver or gold without any other colors on it. They don't get their hair colored in wild shades even if they want to. They wear very soft makeup shades...they'll wear red lipstick because they think "lipstick is supposed to be red" - and be terrified every time they put it on - but their eyes are always done in very soft, muted shades. OF COURSE their cars are going to be in dull, muted colors! I have put companies' corporate colors on print jobs and had the customers get scared that there was "too much color" on the job.

Reason 4: because it's cheaper to paint cars those four colors and people are afraid of color anyway, manufacturers make most of their cars in these forgettable colors. I drive a Volkswagen Tiguan, and when I bought it new I told the sales manager I didn't want a black, white or silver one. (They found me a red one.) I was informed at that time that Volkswagen divides Tiguan production into four batches: one-quarter of them are black, one-quarter are white, one-quarter are silver and the rest are divided up among every other color they make.