Mine had green caps on the tire valves when I picked up the car with the original caps in the glove box. Green sticker on the inside of the windshield with the dealer logo stating that the tires were nitrogen filled.
The nitrogen fill was part of their prep and no extra charge so it didn't matter to me either way. When they need air, I'll just put regular air in them.
13 VR 2SS/RS 1LE (sold)
01 Z28 M6 HT