It all started a few hundred years ago in the Canadian wilderness with 'Rogers rangers' he worked for the brits keeping the Hudson bay company working on the river trading routes
He found the natives would blend in with there surroundings & so copied them which was better than the usual bright colours of the British army, like alot of things, the British ministry dismissed it but got back on board after everyone else
Khaki green came into being during WW1 when it became trench warfare and made it harder for snipers