I can't be sure about any of this, but from what I can find, five SH-3As from HS-2 aboard Hornet were field modified in 1965 to take out the sonar gear and add machine and/or mini-guns, armor plate and fuel tanks in the cabin for added range/time on station - first two 55 gallon drums and then two A-4 centerline drop tanks. At some point, at least one of them got a camouflage paint scheme similar to the USAF: dark green and tan and light gray on the bottom. It was marked with a large black "70" on the nose. The others may have been marked 66 through 69, all markings in black.
Sikorsky developed and qualified the combat rescue specific HH-3A a few years later, converting one aircraft and producing kits for at least nine others, which were modified by the Navy. (Different sources cite different quantities of HH-3As, possibly including the original SH-3As.) Initially, the HH-3A had minigun barbettes mounted on the aft torpedo racks and drop tanks mounted inboard of the main landing gear. This aircraft is pictured in Squadron/Signal's H-3 Sea King In Action. However, the barbettes were heavy, possibly caused an aft CG problem, and probably not very accurate, so they were reportedly deleted before the aircraft went into combat and replaced by miniguns in the doors. At least a few of the aircraft had the aft fuselage windows associated with the RH-3A minesweeping conversion, probably for use by the gunners operating the barbettes, but they may have simply been former minesweepers, of which by coincidence there were nine. The HH-3As were operated by HC-7 beginning around 1971 and transferred to a reserve unit, HC-9, after the war in about 1975. I've seen color photos of them in painted overall dark green with black markings taken during their HC-9 years, but I can't rule out a very non-specular engine gray finish during the Vietnam war.