Well, when I'm doing brush-work using Polly-S paints, I use Soviet Armor Green.
Seems simple enough.
But in truth, it is a bit on the gray side compared to the color I use most often, which is Testors Model Master Medium Green (in a spray can).

These are some T-60s I re-hab'd recently using Poly-S Soviet Armor Green. I bought these in a bucket 'o tanks from a gamer one weekend. I'm not even sure they are GHQ -- maybe the "other guy's". I never did post 'em up on the "Show Us Yer Stuff" thread. They were in pretty tough shape with bent barrels, missing turrets, and all painted a green that was far too dark for my tastes.

I straightened the barrels, and rather than stripping and re-painting from the ground up, I just did a heavy dry-brushing with Soviet Armor Green, and then dry-brushed again lightly with Sahara Sand (a very light beige-green). Never even did a dark wash. Then detailed them, and they were done. Came out pretty nice.

Here, for comparison, are some actual GHQ T-60s that I painted in my more common color set a couple years back. These have been primed white, then sprayed Medium Green, then black washed, then dry-brushed with Sahara Sand, and then detailed.
The lighting isn't identical, but the pics give you a pretty close view of the differences.