Good question. I bought new for the first time recently and found it hard to believe how many people appear to be willing to pay £500+ just for a colour (and one they’ll barely see when using the car). Sure, I have preferences, but not ones I’m willing to put actual money on.
In the U.S. car buying is much more like an old world bazaar than a modern transaction. Dealers might knock this fee off to get you to sign.
Hmm, clever: back down by £500 on the sticker that has zero production cost.
It used to be that grey was often the metallic paint, more durable, and was more expensive than all others, and you'd only find it on 'business class' cars. Now they all have the same qualities.