Like Couper93, painted mine Hi-Gloss Black, with 3 coats of clear.
This spring, while installing the 20" back, had to do a little touch up.

Looks nice on my Black X5

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2010 X5 35d Black - Full (current)
2012 X1 28i (retired, won't be missed)
2007 335i sedan (retired, and missed)