I think you see a lot of boring colors b/c people don't really give a damn about their car anymore...aside from the badge.
Its one of several symptoms that plague the industry today. First off, many cars look very similar. Long are the days where you can name a car from a mile away. Now, most 4-doors share the same profile, shoulders, and proportions. From the side, it's difficult to name who manufactured what. Many look generic. So why not have generic colors?
Furthermore, women & beta males do not take care of their cars. It's why they put little sparkles in black paint; so it looks shiny, somewhat at least, after it hasn't been washed all summer. Likewise, it's also why some cars are sold w/o a dip-stick, with ever-fill fluids, and idiot lights to remind you to go to the dealer for a service. People don't take care of their cars nor do they understand how they work.
An iPhone? You can run into a number of 'experts' on that. But if a car is making a funny noise? Forget it...
People are indifferent so they sell indifferent, un-offensive, and happy-sparkly colors.