I think that this guy's research was about the most thorough that anyone has done - New Page 1

If you take time to find it he says that the paint on the coupe was DuPont #5248A, which is a 1972 Corvette Canary yellow, Centari enamel. That goes against several American Graffiti blogs out there that say "Canary Yellow Lacquer" sprayed by the Orlandi's Body Shop in San Rafael, CA. Now I cannot say what paint your Timeless shop used, but that's the one that's said to be the true color.