A lot of it is due to the dealership model. The dealership doesn't have room for infinite inventory, so they only order vehicles that will appeal to a wide audience. Some buyers will not take a yellow car or a blue one, but very few people will reject a grey car that otherwise meets all their requirements. So we end up with: white, white-grey, off-grey, grey, dark grey, bold grey, charcoal, and black.

Interesting to note, if you go look at the 'build your own' options on a manufacture's website, they do still offer colors. But it can be surprisingly difficult to get, as you ultimately have to order through the dealership. The dealership is much more motivated to sell you what's on the lot today, rather than let you order a car that will arrive in 6 months.

Also, my mother calls this year's grey "mud grey", which I find very funny for some reason.