Paint companies can also pull up paint formulas by make/model/year and location on the car, etc. If you go to
http://colorexplorer.rmpaint.com/index.php they only show one wheel paint formula for a 2008-2013 BMW M3 which is code# 20304.
If you cross reference the individual paint codes on that calculator against the RM Diamont Line on this site
http://www.autobodysupply.net/SearchResults.asp you will see that formula is for paint that is 34% black, 28% mica white, 11% metallic flake, 7% normal while, 3% gold, 2% blue, and then some other various things. So my guess this color is for the 219 wheels, or possible for the gray between the spokes of the 220 wheels.