That probably depends a lot on where you are. In large parts of the Bay Area expensive cars are ridiculously common and while I haven't gathered any actual data

That probably depends a lot on where you are. In large parts of the Bay Area expensive cars are ridiculously common and while I haven't gathered any actual data, my impression is that neutral colors are nearly as common for luxury vehicles as they are for normal vehicles. Seriously, a white/black/grey/silver Model S/X, RX/NX, X5/X3, GLC/GLE, Cayenne, etc. is a ubiquitous "soccer mom" vehicle around here. Of course you will also see your brightly colored 911s and similar. Oh, and those new (I think?) mid-engine Corvettes are everywhere.