I'd go with matte black, to match the body trims and bumpers. That combo looks pretty good on an Imola Red E39 M5, so I can't see why it wouldn't look good on an Imola Red 4.6.

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2003 X5 4.6 | 2000 540i Touring

Formerly owned:
2004 Range Rover | 2000 M5 | 2000 540i/6
1995 750il | 2003 Mercedes S500 | 2003 540i/6