Animal coloration provided important early evidence for evolution by natural selection, at a time when little direct evidence was available. Three major functions of coloration were discovered in the second half of the 19th century, and subsequently used as evidence of selection: camouflage (protective coloration); mimicry, both Batesian and Müllerian; and aposematism.

Charles Darwin's On the Origin of Species was published in 1859, arguing from circumstantial evidence that selection by human breeders could produce change, and that since there was clearly a struggle for existence, that natural selection must be taking place. But he lacked an explanation either for genetic variation or for heredity, both essential to the theory. Many alternative theories were accordingly considered by biologists, threatening to undermine Darwinian evolution.

Some of the first evidence was provided by Darwin's contemporaries, the naturalists Henry Walter Bates and Fritz Müller. They described forms of mimicry that now carry their names, based on their observations of tropical butterflies. These highly specific patterns of coloration are readily explained by natural selection, since predators such as birds which hunt by sight will more often catch and kill insects that are less good mimics of distasteful models than those that are better mimics, but the patterns are otherwise hard to explain.

Darwinists such as Alfred Russel Wallace and Edward Bagnall Poulton, and in the 20th century Hugh Cott and Bernard Kettlewell, sought evidence that natural selection was taking place. Wallace noted that snow camouflage, especially plumage and pelage that changed with the seasons, suggested an obvious explanation as an adaptation for concealment. Poulton's 1890 book, The Colours of Animals, written during Darwinism's lowest ebb, used all the forms of coloration to argue the case for natural selection. Cott described many kinds of camouflage, and in particular his drawings of coincident disruptive coloration in frogs convinced other biologists that these deceptive markings were products of natural selection. Kettlewell experimented on peppered moth evolution, showing that the species had adapted as pollution changed the environment; this provided compelling evidence of Darwinian evolution.

Charles Darwin published On the Origin of Species in 1859, arguing that evolution in nature must be driven by natural selection, just as breeds of domestic animals and cultivars of crop plants were driven by artificial selection. Darwin's theory radically altered popular and scientific opinion about the development of life. However, he lacked evidence and explanations for some critical components of the evolutionary process. He could not explain the source of variation in traits within a species, and did not have a mechanism of heredity that could pass traits faithfully from one generation to the next. This made his theory vulnerable; alternative theories were being explored during the eclipse of Darwinism; and so Darwinian field naturalists like Wallace, Bates and Müller looked for clear evidence that natural selection actually occurred. Animal coloration, readily observable, soon provided strong and independent lines of evidence, from camouflage, mimicry and aposematism, that natural selection was indeed at work. The historian of science Peter J. Bowler wrote that Darwin's theory "was also extended to the broader topics of protective resemblances and mimicry, and this was its greatest triumph in explaining adaptations".

In his 1889 book Darwinism, the naturalist Alfred Russel Wallace considered the white coloration of Arctic animals. He recorded that the Arctic fox, Arctic hare, ermine and ptarmigan change their colour seasonally, and gave "the obvious explanation", that it was for concealment. The modern ornithologist W. L. N. Tickell, reviewing proposed explanations of white plumage in birds, writes that in the ptarmigan "it is difficult to escape the conclusion that cryptic brown summer plumage becomes a liability in snow, and white plumage is therefore another cryptic adaptation." All the same, he notes, "in spite of winter plumage, many Ptarmigan in NE Iceland are killed by Gyrfalcons throughout the winter."

More recently, decreasing snow cover in Poland, caused by global warming, is reflected in a reduced percentage of white-coated weasels that become white in winter. Days with snow cover halved between 1997 and 2007, and as few as 20 percent of the weasels had white winter coats. This was shown to be a result of natural selection by predators making use of camouflage mismatch.

In the words of camouflage researchers Innes Cuthill and A. Székely, the English zoologist and camouflage expert Hugh Cott's 1940 book Adaptive Coloration in Animals provided "persuasive arguments for the survival value of coloration, and for adaptation in general, at a time when natural selection was far from universally accepted within evolutionary biology."