Mark Reynosa's book on the M1 helmet states that other services drew M1 helmets as an entire issue (pot, liner, susupension, chin straps, etc.) from Depots by purchase order. That presumes they would be in the factory-applied OD paint until they got to their end users.
Most of our Repair Party pots were OD under the Red paint we put on them. In WWII, an operational Peter Tare far from by-the-book types might could have any color helmets.
The WWII kapok I scored in a long-ago trade is about halfway between gunship and panzer grey in color. I've seen them faded to near 5N, and the seams most of white--but those were also close to falling apart, too.