I think this aircraft is in unpainted metal - the areas which appear grey are probably just down to the image quality. The rudder will have green and yellow vertical stripes on it but the b&W film used probably did not differentiate well between the two colours.
See my other post in this topic for a link to more information. Oh, and judging from the fact that the aircraft is on its nose while still on the ramp, I'd guess that someone ran the engine up to too high a manifold pressure when they were testing the magnetos...OOPS!