It's plastic wrap. I've seen Rick wrap the tires after he applies the painted codes on the tires. The wrap protects the markings and keeps dirt and pebbles from getting into the tread so the tires are 'show ready' when the car is shown to the customer for the first time, or when it's unveiled at a show.
Rick is a detail nut bordering on analism!
If he treats the tires with kid gloves, just imagine what little secrets lie hidden in other areas!
