I have always used Testors Dark Green FS #34079 for all my Russian Armor. It is so close to the Russian Green that shows on my Testors Color Chart that no one can tell the difference. Besides, as others have mentioned, the shade never stays the same. If you wish to see some of my Russian Armor, check this link:
http://f1.pg.briefcase.yahoo.com/commander_markez
Look under the Armor folder, and you'll see about 15 Russian tanks and trucks all painted in Dark Green. All are also in 1/72 scale too.