Did you notice when you look at that pile of old cars you see many different and nice colors.
Now all modern cars are practically the same color and only a few have nice colors like most older cars had. The black car my wife drives is nice but we wanted it in red or orange but those colors were not options.
My dad used to tell me that automobiles were shifting from more exciting colors and designs to less offensive and I think he was right. Most of the models you see look roughly the same both in design and color. I'm pretty sure some surveys figured out what the safest shapes and colors were and they ran with it.