The US Marines were famous for wearing the P42 “Frog skin” camouflage in mid WWII but it went as quickly as it came it seems and we don’t see wide spread official camouflage adoption until late in Vietnam. That doesn’t mean that it wasn’t still being used all be it in very limited numbers. Here are some seldom seen pictures of camo being worn during the Korean War. I believe all are from the 1st Recon Battalion.
This last one should be from a series of LIFE photography from around the time of the Inchon landings to the second battle of Seoul by Carl Mydans,