To the best of my knowledge, PAVN tanks were painted in the same khaki green colour they received them in from the Soviet Union (typically KhS-508). In the case of Chinese supplied vehicles, the Chinese local equivalent. MiG produce a variety of post-war Soviet greens if you are especially anal about such things.
To be honest there's little point getting too hung up about exact shades as in practice they varied quite wildly for a variety of reasons including batch differences, manufacturer's differences, sun exposure and environmental factors, ie mud, dust,oil stains etc, etc. By the time you have weathered the vehicle up pretty much any darkish olive green will do the job, including 4BO, the WW2 era Soviet Green.
I've tended to use a variety of Tamiya rattle can greens, including NATO green. Whilst I can't claim they are 100% historically accurate, I've been fortunate enough to examine a number of PAVN vehicles in museums in Hanoi and HCM City/Saigon and I'm happy enough with the Tamiya rattle can approach. I can post photos of the originals and my interpretations if you like.