The only paint between the doors, hinges & jambs would be the various stages of "dip seal" which is often - you guessed it - GREEN. There was no stock pile of painted bodies looking for an identity, as that body was assembled it was done to instructions to build Shipping Order #772811. '68 Coronets were painted with the complete body assembled.

This Coronet R/T's complete identity was attached to #772811 before it was VIN sequence #169291.

WAG
I could see a plant manager, exec., or other making "handshake" arrangements for special handling (non-standard rust treatments etc.?) while their next car was going down the line, but doesn't make too much sense for a car they would be in possesion of for 120 days (unless you find Mr. McCartney worked for Chrysler?). Maybe they had special procedures for "Company Cars"?