The probability that anybody knows the real answers is pretty much zero.

In the case of my torsion bars, the original factory paint and factory paint daubs are still plenty good enough as-is for a thorough restoration.

All the photos I've seen and the paint daubs on my own leaf springs indicate these were made with latex paint in pastel house paint colors.

Go to Lowe's and buy two half pint sample colors of exterior grade for less than $10. Pick your colors from the dozens of brochures on display.

In my case, the colors looked to me like khaki tan and aqua, which translated to Sherwin Williams Balanced Beige and Transparent Pool. But there were numerous other choices that would have worked just as well.

Be sure to apply the latex before the RPM wax. Oops.