I wasn't a firm believer of the painted black front springs either. My San Jose convertible seemed to have a dark steel (like the steering parts) finish instead of black paint. However, the 67 Metuchen coupe that I am doing now seems to have black painted springs. After soaking the springs in evapo-rust, I carefully removed sections of the colored stripes (evapo-rust doesnt always remove paint) with a razor blade only to find black paint on the back side of the color stripe paint. Granted I didn't do a paint analysis to 100% verify it was paint, but I did attempt to scrape areas on the springs other than where the paint stripes were and did not get the same results as under the stripes. Also, there appeared to be thicker paint on the top of the spring...like it was dipped and then set on the flat top part to dry.
Oh, and the front sway bar on this car also was painted black. Just some Metuchen plant observations...
Regards,
Pete Morgan