I think you are correct on the Hugger Orange full size and Corvairs. While seen often on Camaros I don't really remember any Chevelles, but this was still a time when you could special order just about any GM color on any GM car. The HG Chevelles would make since I remember more than one El Camino in that color. I think the color came available after the first of the year for Pontiac Judges. I knew a guy who ordered a '69 Judge and he had to wait till the new year, calendar 1969, before they would release it to build. Something about the Monaco Orange makes me think the color is slightly different shade. You mention the Red color on Chevrolets, in addition to the Garnet Red they did in fact have a bright non metallic Red also.