Short answers, pulled from the story.
Charles Darwin published his theory explaining the evolution of features like camouflage in 1859. This process enabled creatures to leave more offspring on average than other members of the same species.
Abbott Handerson Thayer formulated what is sometimes called Thayer's Law, the principle of countershading, in his 1909 book Concealing-Coloration in the Animal Kingdom. He argued that all patterns and colors whatsoever of all animals that ever preyed or are preyed on are under certain normal circumstances obliterative.
Two Napoleonic War skirmishing units of the British Army, the 95th Rifle Regiment and the 60th Rifle Regiment, were the first to adopt camouflage in the form of a rifle green jacket. A contemporary study in 1800 by the English artist and soldier Charles Hamilton Smith provided evidence that grey uniforms were less visible than green ones at a range of 150 yards.
Andy Warhol began a series of monumental camouflage paintings in 1986 which helped to transform camouflage into a popular print pattern. A year later in 1987 New York designer Stephen Sprouse used Warhol's camouflage prints as the basis for his Autumn Winter 1987 collection.
The first genuinely digital camouflage pattern was the Canadian Disruptive Pattern CADPAT issued to the army in 2002. Soon followed by the American Marine pattern MARPAT with a pixellated appearance though this effect is not essential for the result.