Gray-green is tricky. I have some familiarity with grigio-verde in person, and have been to enough reenactments to have a good understanding of the difficulties.
The cloth is basically a "heather" (not sure if that's the right term) -- different batches of wool were dyed in different colors (gray and green), then were spun together into threads, then woven into cloth. Up close you will notice different colored blotches, but they blend together at a short distance.
The effect is impressive. Even in person, the lighting will affect how it appears, sometimes looking more gray, sometimes more green, sometimes more brown. The lighting can have an even more dramatic effect when photographed, if it's not carefully controlled. Then there are the natural variations that occur with wool dying, compounded by war time shortages.
Trying to match that color in paint is therefore tricky, and kind of open to interpretation. In my opinion, most of the time the uniform "plates" failed almost completely, and instead of an accurate portrayal of the color are just the artist's attempt to distinguish the wool color from other colors on the equipment, etc., without being too confusing.
I think you've done a decent job, I might even go a little greener for early war feldgrau.
