Color reflected color depends upon the viewing angle. Numerous scientists have carried out research in butterfly wings and beetle shells, including Isaac Newton and Robert Hooke. Since 1942, electron micrography has been used, advancing the development of products that exploit structural color, such as "photonic" cosmetics. Color Color (American English), or colour (Commonwealth English), is the characteristic of human visual perception described through color "categories", with names such as red, orange, yellow, green, blue, or purple. This perception of color derives from the stimulation of cone cells in the human eye by electromagnetic radiation in the visible spectrum. Color categories and
Orange (colour) of extremes, trying to make the colours intense, and not a harmony of greys." In the 20th and 21st centuries, the colour orange had highly varied associations, both positive and negative. The high visibility of orange made it a popular colour for certain kinds of clothing and equipment. During the Second World War, US Navy pilots in the Pacific began to wear orange inflatable life jackets, which could be spotted by search and rescue planes. After the war, these jackets became common on both civilian and naval vessels of all sizes, and on aircraft that flew over water. Orange was