Well it doesn't come in hotrod red, but it does come in camo.
Most probably, my next take on the Tumbler will be to adapt a retractable turret on the rooftop, as seen in the upcoming "The Dark Knight Rises" movie. Just for now, the "standard" version will do.
Check my photostream for more pictures on the Tumbler.
The building instructions set for the Tumbler is available on Brickshelf. Make sure you check the images in their original size for best view on details and building notes.