Primer color

[Ronw435]

Was wondering if anyone can tell me what the original color of primer was for our trucks? I am posting a couple of pics that show a red primer under the paint. When sanding it there is nothing but metal underneath. I have used paint stripper on it and it will take the top paint coat off but really doesn't not do much with the primer.
In the places under panels where the original (I think) color is there is red primer under that as well.

Any ideas?

Ron