I'm sure the Dart will look great whatever color you decide to paint it. In the 67 Dart factory sales brochure, the convertible shown in the brochure is medium copper metallic like your car. Someone here should have that factory photo on line.
I found a site showing the factory brocure but there were no copper colored convertibles in it.Maybe you were thinking of this advertisement which shows a convertible in a gold metallic color: