It started with a simple question, "What Vallejo colour do I use as the base colour for Russian WWII tanks?" Plastic Soldier Painting Guide for my T70 and T34 says "Russian Green" [Vallejo Model Colour 70.894 which seems to make sense] but I got slightly more than I bargained for from my You Tube search.
Helpful videos from You Tube, with excellent tutorials and painting results:
The results from these videos are fantastic and mean that I will have to start weathering my models. The answer to my original question I think is: Vallejo Model Colour 71.017 (Russian Green 4BO) - which may be an air brush colour anyhow, for the professionals .. but I will have to made do with Vallejo 70.894 (see below, when did life become so complicated and I get the feeling that I should not really "care" that much?):
Bring me a Russian WWII tank to paint while I an still of sound mind! I will work on the principle of two thin coats is better than one thick!