What color primer was used

My car, a 65 Dart built at Hamtrak, has red oxide under the outer body panels. I don't remember seeing the greenish primer but it could have been there. The car has been painted a couple of times.

The bottom of the car is nothing but the dark gray it was dipped in. The interior floor and inside the trunk has the same dip primer under the paint. The engine compartment and firewall has either black or dark gray under the body color paint. I'm pretty sure I saw red oxide in the fender wells under body color paint. But I don't see how these wouldn't also have the dark gray dip. There could very well have been dark gray under the red oxide. Up behind the dash seems to have a light coat of red oxide with nothing over it.

An advantage of using a darker color for you base coat is that you can tell when you're starting to sand through the filler primer. I'll be using black under the car and red oxide on the outer panels for my epoxy primer. Then I'll use a light gray filler primer.