i have paint peeling off the steprails (pretty common- same stuff as the roofrack). i unscrewed the plastic 'steps' and man, it is all jacked up under there. paint chipped and missing in huge chunks.
like others said, doesnt matter- its alumimum. someone mentioned a krylon or rustoleum spray paint that was close match...cant remember now. try searching for that thread.
from the looks of the chips, they did not properly prep the aluminum before painting, did not primer or the powdercoat was electrostatically done without primer (not my theory). whatever it is, its obviously not a good bond to the aluminum.