Do a Search on Yahoo for
WWII Blankets
and you will get a few pages that have pics of them mostly for sale..
any green color from a light khaki green to a darker field green would work..
a couple of my favorite Model Master colors for GI equipment is Faded Olive Drab and Feild Drab (which I lighten a bit.)
after basecoat i would wash with a darker green then drybrush with a lightened color of the basecoat.
since these faded with time and use almost no color green would be the Exact Green so feel free to experiment.