Sorry I haven't made myself heard in here earlyer... Kind of busy lately...
Well, the Swiss Army has painted its tanks in this one tone color all through the cold war and changed to standard 3-tone NATO camo in the 90ies, with some vehicles remaining in the old scheme well in to the 21st century (like older M109 and M113). Softskins are still in that color actually. Tones also depended on where the vehicles was originally from (M113 and M109 hat a more US-OD color for example) and how long it had been in "action" (fading etc.).
It is hard to tell the right color, especially from old pics and restored vehicles
If you check these pics:
http://www.panzerbaer.de/types/pix/ch_jgdpz_hetzer_g13-007.jpghttp://www.panzerbaer.de/types/pix/ch_jgdpz_hetzer_g13-008.jpg it looks like more a grey-green color. That is also the way I remember it from preserved vehicles and the soft skins we still use. Older vehicles I have served on (Like the Steyr-Daimler Puch) tended to be more grayish.
So on your model Olivier, I probably would try to tone down the green a bit and make it more grayish. You can get more of an idea by googling pics for early cold war Swiss armor (the AMX-13, Centurion, Pz. 68 and G13).
So, maybe some other Swiss modelers will want to chime in?
Cheers!
Stefan