When I was in the Navy ('87-'92), our wool blankets were grey, with a black "US" stenciled on them. They were quite warm... I remember spending a night on USS Papago while in drydock. The side of the ship had been removed so the engines could be changed out, and it was winter in Virginia. It got down into negative temperatures Fahrenheit that night, but about six of those blankets bundled around me kept me toasty warm all night.