If the footage you saw was of new models being tested, then yes, most of the early jets were unpainted. This continued for a few years with operational units as well. Jets were the new supertechnology, and didn’t need anything as pedestrain as camouflage: the only thing that could bring them down was other jets.
But as with the advent of the SAM, jets were once again vulnerable to ground fire. Camouflage came back - look at Air Force F-105s and F-4s over in Vietnam. Light gray on the bottom, dark green and brown on the top. Even the F-100 Super Sabre, which started out unpainted ended up with camouflage when it went into action.
As aircraft missions became more specialized, so did the paint. F-15s have sported various mutations of gray their entire lives, since they are air superiority fighters only. The F-15E, designed as a night attack bomber is painted very dark grey. F-111s carried green/brown camouflage for most of their career.
In the early 90s the Air Force went to a gray paint scheme for almost every aircraft. We joked that it was “air superiority” gray (we were flying C-141s, big lumbering transports). Almost every airplane got this treatment - KC-10s, C-5s, C-17s, even A-10s. About the only thing left untouched were trainers and VIP aircraft.