Even earlier in history, Julius Caesar supposedly had a ship painted to match the color of the water. Even the sails blended with the surroundings. He wanted the crew to gather information as stealthily as possible when they sailed along the coastline.
After discovering that Caesar used camouflage tactics, it's a good guess that they've been around longer than written history.
Photo above: Camouflaged tree frog who made me think he knows what he looks like even without a mirror.