Military camouflage
The emphasis on hand-to-hand combat, and the short range of weapons such as the musket, meant that recognition and cohesion were more important than camouflage in combat clothing well into the baroque period. The introduction of infantry weapons with longer range, especially the Baker rifle, opened up new roles which needed camouflaged clothing. In the colonial Seven Years' War (1756–1763), the rifle-armed Rogers' Rangers wore gray or green uniforms. John Graves Simcoe, one of the unit's later commanders, noted in 1784:

Green is without comparison the best colour for light troops with dark accouterments; and if put on in the spring, by autumn it nearly fades with the leaves, preserving its characteristic of being scarcely discernible at a distance.

The tradition was continued by British Rifle Regiments who adopted rifle green for the Napoleonic Wars.
During the Peninsular War, Portugal fielded light infantry units known as Caçadores, who wore brown-jackets which helped conceal them. The brown color was considered to be more adequate for a concealment in the landscape of most of Portuguese regions, in general more arid than the greener landscapes of Central and Northern Europe. Other nations soon followed suit, dressing their rifle regiments and sometimes also light troops in suitable drab tones, usually variations of green or gray.
The first introduction of drab general uniform was by the British Corps of Guides in India in 1848. Initially the drab uniform was specially imported from England, with one of the reasons being to "make them invisible in a land of dust". However, when a larger quantity was required the army improvised, using a local dye to produce uniform locally. This type of drab uniform soon became known as khaki (Urdu for dusty, soil-coloured) by the Indian soldiers, and was of a similar colour to a local dress of cotton coloured with the mazari palm. The example was followed by other British units during the mutiny of 1857, dying their white drill uniforms to inconspicuous tones with mud, tea, coffee or coloured inks. The resulting hue varied from dark or slate grey through light brown to off-white, or sometimes even lavender. This improvised measure gradually became widespread among the troops stationed in India and North-West Frontier, and sometimes among the troops campaigning on the African continent.

Rifle fire: While long range rifles became the standard weapon in the 1830s, armies were slow to adapt their tactics and uniforms, perhaps as a result of mainly fighting colonial wars against less well armed opponents. Not until the First Boer War of 1880/81 did a major European power meet an opponent well equipped with and well versed in the use of modern long range repeating firearms, forcing an immediate change in tactics and uniforms. Khaki-coloured uniform became standard service dress for both British and British Indian Army troops stationed in British India in 1885, and in 1896 khaki drill uniform was adopted by British Army for the service outside of Europe in general, but not until the Second Boer War, in 1902, did the entire British Army standardise on khaki (officially known as "drab") for Service Dress.
The US military, who had blue-jacketed rifle units in the Civil War, were quick to follow the British, going khaki in the same year. Russia followed, partially, in 1908. The Italian Army used grigio-verde ("grey-green") in the Alps from 1906 and across the army from 1909. The Germans adopted feldgrau ("field grey") in 1910. By the outbreak of the First World War in 1914, France was the only major power to still field soldiers dressed in traditional conspicuous uniforms.

The First World War: The First World War was the first full scale industrial conflict fought with modern firearms. The first attempt at disruptive camouflaged garment for the French army was proposed in 1914 by the painter Louis Guingot, but was refused by the army, which nevertheless kept a sample of the clothing. In collaboration with a Russian chemist friend, Guingot had developed a process of painting on weather-resistant fabric before the war and had registered a patent for it. But the casualty rate on the Western Front forced the French to finally relinquish their blue coats and red trousers, adopting a grayish "horizon blue" uniform.

The use of rapid firing machine guns and long range breech loading artillery quickly led to camouflaging of vehicles and positions. Artillery pieces were soon painted in contrasting bold colours to obscure their outlines. Another early trend was building observation trees, made of steel with bark camouflage. Such trees became popular with the British and French armies in 1916. The observation tree was invented by French painter Lucien-Victor Guirand de Scévola, who led the French army's camouflage unit, the first of its kind in any army. He also invented painted canvas netting to hide machine gun positions, and this was quickly taken up for hiding equipment and gun positions from 1917, 7 million square yards being used by the end of the war.
The First World War also saw the birth of aerial warfare, and with it the need not only to conceal positions and vehicles from being spotted from the air, but also the need to camouflage the aircraft themselves. In 1917, Germany started using a lozenge camouflage covering Central Powers aircraft, possibly the earliest printed camouflage. A similarly disruptive splinter pattern in earth tones, Buntfarbenanstrich 1918, was introduced for tanks in 1918, and was also used on the Stahlhelm (steel helmet), becoming the first use of a standardized camouflage pattern for soldiers.

Camoufleurs: In 1909 an American artist and amateur zoologist, Abbott Thayer published a book, Concealing-Coloration in the Animal Kingdom, which was widely read by military leaders, although his advocacy of countershading was unsuccessful, despite his patent for countershading submarines and surface ships.
The earliest camouflage artists were members of the Post- Impressionist and Fauve schools of France. Contemporary artistic movements such as cubism, vorticism and impressionism also influenced the development of camouflage as they dealt with disrupting outlines, abstraction and colour theory.The French established a Section de Camouflage (Camouflage Department) at Amiens in 1915, headed by Lucien-Victor Guirand de Scévola. His camoufleurs included the artists Jacques Villon, André Dunoyer de Segonzac, Charles Camoin and André Mare.
Camouflage schemes of the First World War and Interwar periods that employed dazzle patterns were often described as "cubist" by commentators, and Picasso claimed with typical hyperbole "Yes, it is we who made it, that is cubism". Most of the artists employed as camoufleurs were traditional representative painters, not cubists, but de Scévola claimed "In order to deform totally the aspect of the object, I had to employ the means that cubists use to represent it."
Other countries soon saw the advantage of camouflage, and established their own units of artists, designers and architects. The British established a Camouflage Section in late 1916 at Wimereux, and the U.S. followed suit with the New York Camouflage Society in April 1917, the official Company A of 40th Engineers in January 1918 and the Women's Reserve Camouflage Corps. The Italians set up the Laboratorio di mascheramento in 1917. By 1918 de Scévola was in command of camouflage workshops with over 9,000 workers, not counting the camoufleurs working at the front itself. Norman Wilkinson who first proposed dazzle camouflage to the British military employed 5 male designers and 11 women artists, who by the end of the war had painted more than 2,300 vessels. French women were employed behind the lines of both the British and American armies, sewing netting to disguise equipment and designing apparel for soldiers to wear.

From the Second World War: Printed camouflage for shelter halves was introduced for the Italian and German armies in the interwar period, the "splotchy" M1929 Telo mimetico in Italy and the angular Splittermuster 31 in Germany. During the War, both patterns were used for paratrooper uniforms for their respective countries. The British soon followed suit with a brush-stroke type pattern for their paratroopers' Denison smock, and the Soviets introduced an "amoeba" pattern overgarment for their snipers.
Hugh Cott's 1940 book Adaptive Coloration in Animals systematically covered the different forms of camouflage and mimicry by which animals protect themselves, and explicitly drew comparisons throughout with military camouflage:

The principle is one with many applications to modern warfare. In the Great War it was utilized by the Germans when they introduced strongly marked incidents of white or black tone to conceal the fainter contrasts of tone made by the sloping sides of overhead camouflage-screens, or roofing, as seen from the air. The same principle has, of course, a special application in any attempt to reduce the visibility of large objects of all kinds, such as ships, tanks, buildings, and aerodromes.
Both British and Soviet aircraft were given wave-type camouflage paintwork for their upper surfaces throughout the war, while American ones remained simple two-colour schemes (different upper and under sides) or even dispensed with camouflage altogether. Italian and some Japanese aircraft wore sprayed-on spotted patterns.