Maybe people prefer (red, green, bright blue), but they fear that they won't be able to sell their car because of its color. So they buy white.
(I read somewhere [so take this with a grain of salt] that this effect happens with marble kitchen countertops: not that many homeowners actually like them, but they believe that potential buyers might, so an overproportional amount of people put them in their kitchens - leading everybody else to believe that they're actually very popular.)