FC7 Plum Crazy Purple paint question

I took my 70 Swinger C7 car down and I could almost swear it was red primer but it was 18 years ago so...
Some are red oxide primer. That is what the bodies all had on them. Most were primered gray over that but I have seen some that were not. The gray was never that thick and usually was the cause of the paint flaking off. When ever you would see a car with the paint coming off it was usually down to the red oxide