Actually they are steel gray. I broke the tabs off of my Imola Red caps (I'm a genius, it's confirmed). I kinda like them grey but will most likely end up painting them gloss black (my reason for removing the imola caps and breaking their tabs).
Dark grey, silver and black caps seem to be a new trend with new BMW's. I think the black would blend in with the gloss black window trim and tinted windows.
--Marcus