My orange 72 (6/72) 24k mile original paint 240 has a light application of undercoat with factory orange paint on top. It is a light topcoat but more intentional than over spray. I can't be sure whether there is primer under the undercoating or not. I have the car mostly disassembled refreshing it so the undercarriage is stripped of all hardware, drivetrain, suspension, fuel/brake lines, etc, etc. My plan is to keep the original paint. I am detail cleaning the dirt from the undercarriage and plan to touch up any areas where the paint/undercoating has chipped away to expose metal (none so far but will use primer, light amounts of undercoating and touchup paint from automotivetouchup.com). So far, I have only cleaned the wheel wells and the suspension / fuel tank areas of the rear. While I haven't cleaned the tunnel, the tunnel is undercoated lightly also but the orange paint seems to fade away and I doubt that cleaning will reveal any orange paint like it has in the other areas of the undercarriage.