Halogen. No Z3 ever came with Xenons from the factory. Those weren't offered as an option on a Roadster until the debut of the E85 in 2003.

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-Dusty
2007 X3, Montego Blue
1998 Z3 Roadster, Montreal Blue
1996 Z3 Roadster, Jet Black
2016 Miata LE, Soul Red
1981 DeLorean, Stainless Steel
1979 Ferrari 308 GTS, Ocean Blue