Polyurethane Dip Gray Primer Dip Gray underbody on your car is correct.
The topside was first primed with a red oxide primer, followed by a light gray primer. Last was the topcoat color obviously. Some of the red oxide, light gray primer & topcoat color would overspray under the body; how much varied greatly... some cars show very little if any of the red or light gray primers and I've seen less common examples where it looked like the painter was using a garden hose applying the red oxide.
If you're lucky enough to have pics of, or the original example to go by, study it carefully for the best reference you can get!