When I bought the GTR in '80, it was painted a dull black which certainly didn't look original. I stripped that off and went to the local parts store. I don't think I have any notes or dried paint can remaining, but I think the metallic blue was some late '70s Chevy color that looked good (to me) on a paint chip. It was also missing one exhaust core, so we pulled the other one out and used conduit to fabricate one. We knew it'd never rust.