I just came across this today, I saw a 2012 997 C4S with black lug nuts, and the car was brand new, so I did some digging with the local parts department, and Porsche now offers OEM black lug bolts(standard and +5mm) and locking sets. The regular lugs are part number 970-361-203-00, the +5mm length bolt is WHT-004-676-A, and the locking set in black is 991-361-057-01 and the locking set in +5mm is 991-361-980-01. Hopefully these will be an easy solution to the black lug bolt question.