Although this doesn’t discuss artist oil paints, the guy who made the video does go into a lot of detail about the actual nature of “Panzer gray.” If you’re willing to experiment with oils, his description of the ACTUAL hue is illuminating and should provide a good start.
14 Shades of Panzer Gray Paint
If I was trying to mix up a prototype match, I might start with Payne’s gray and add a touch of green and see what happens…