I think this is the same reason home interiors are all painted white or light beige. People are thinking about resale. Any bright color will turn off half of your buyers. A bland, muted color doesn’t turn most people off and is generally ignored. The same goes for the initial car sale. Instead of keeping four of the same model on the lot to cover the major colors, you can keep units that have different sets of functional options. On different note, I recall a study years ago that showed bright colored cars (mainly red) were more likely to get ticketed for speeding by the police. It’s probably worse now that you would be the only red for miles around.