I think this is starting to change, fortunately, with things like the yellow Renault 5s.

Mind you, when ordering a lease car for the first time recently, I did notice that I was paying a premium for non-bland colours. I suspect the weird financial structure of new cars has - they're often not bought to hold, but leased - has a lot to do with the blandness.

There's a large segment of population that will only buy white/black/gray. The paint lines are geared toward those that sell well and special colors are relegated to shorter runs with more expense for changeovers.