I think Dave's on vacation this week, but I'm pretty sure he painted the ONTC figs too.
If I had to guess from looking at a pic (WWII is not my era), keeping in mind there is wiggle room because when exposed to the elements, fabrics can change color a bit, I'd try Military Green, a touch of black, enough white or ivory to lighten it to the tone you want, and experimenting with adding a touch of blue (on my monitor the tunics looks green-gray-blue), and perhaps a little burnt umber. Or it's possible that Vallejo just makes the color straight out. So you can either experiment a bit or wait till next week and call Dave at MichToy. You could also try asking Pete at MichToy. He's switched to acrylics from oils and might be able to point you in the right direction too.