4BO (4БО) paint differ are a middle gray-green, sometimes it are a little darker, very near too dark green/dark gray, so nearly each green and gray can be justified. In WWII, some of the pigment with some oil, gasoline, kerosene or diesel, so there were many colors of the “correct” or “exact” Russian Green:
For some reason I have yet to learn, soviet trucks tended toward sap green. Post war Russian tanks seen in May Day parades seemed to have a definite blue cast. Oddly, mobile missile launchers in the same parades photographed as good old, bad old, crappy “Protective Paint Green, Shade 4BO (4БО)”, aka Russian Green (call it olive).