They were dipped in primer. Resto Rick sells the paint you want to get the factory look, then body color oversprayed on to the dip primer colored paint. I like to use epoxy then resto rick primer look paint on top of that.

68 Road Runner, 69 Belvedere, 71 Challenger Vert
340 barracuda, 01 Ram CTD, 95 Ram, 04 Ram, 85 Daytona turbo Z
66 GTO, 06 Magnum RT AWD. 07 Ram CTD, 07 Ram