I think it's called the splitter, I am talking about the gunmetal grey section at the bottom centre of the bumper like here:

There is a section of the paint that is missing and so the darker colour underneath is showing. Does anyone know this colour code or is it vinyl or something like that? Any ideas on the best way to patch it up?

This photo suggests it's a removable part but I guess it is an expensive part, anyone know the part number and name?