Charles Hamilton Smith Lieutenant - Colonel Charles Hamilton Smith ( 26 December 1776 , East Flanders , Belgium – 21 September 1859 , Plymouth ) was an English artist , naturalist , antiquary , illustrator , soldier , and spy . Military service . His military career began in 1787 , when he studied at the Austrian academy for artillery and engineers at Mechelen and Leuven in Belgium . Although his military service , which ended in 1820 and included the Napoleonic Wars , saw him travel extensively ( including the West Indies , Canada , and United States ) , much of his time was spent at a desk job in Britain . One of his noteworthy achievements was an 1800 experiment to determine which colour should be used for military uniform s . The increasing accuracy of firearm s , especially rifle s , brought advantages to shades which offer a less distinctive target - by testing the accuracy of a rifle company against grey , green , and red targets , he showed scientifically the advantages of grey ( and to a lesser extent , green ) uniforms over red ones common at the time , and recommended that grey be adopted for riflemen and light infantry . The British army did not heed his advice , with green becoming the colour associated with light infantry . Initially commissioned into the 60th Foot , Smith later transferred to the 6th Foot . Antiquary , naturalist and illustrator . As a prolific self - taught illustrator , he is also known in military history circles for " Costume of the Army of the British Empire " , produced towards the end of the Napoleonic Wars and an accurate depiction of contemporary British uniform . As an antiquarian , he also produced , in collaboration with Samuel Rush Meyrick , " Costume of the Original Inhabitants of the British Islands " , 1815 , and " The Ancient Costume of England " , with historical illustration s of medieval knights , ladies , shipsm and battle s . The majority of his vast body of work ( he estimated it was over 38 , 000 drawings ) was not military in character , but largely passed into obscurity . Notebooks of his observations as a naturalist have survived , as well as antiquarian illustrations of civilian life . He also wrote on the history of the Seven Years ' War and the natural history of dogs . Smith was of Flemish origin ; he wrote the military part of Cox ' s " Marlborough " and many military and natural history books . " The Natural History of the Human Species " . Smith published " The Natural History of the Human Species " in 1848 . In this book , he maintained that there had always been three fundamentally distinct human types : the Caucasian , the Mongolian , and the Negro . Smith was nominally a monogenist , maintaining that the creation of humans was single rather than multiple , but he was less convinced by the standard theories of the time coming from Count Buffon and Georges Cuvier on interfertility and species ; the book also referred to the polygenist views held by Samuel George Morton . Smith ' s book was reprinted in America , where Samuel Kneeland wrote an 84 - page introduction to it . Kneeland laid out evidence which he maintained supported polygenist creationism , and argued that the Bible is compatible with multiple Adam s .