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
Judo of national judo associations. The IJF is responsible for organising international competition and hosts the World Judo Championships and is involved in running the Olympic Judo events. Judo is a hierarchical art, where seniority of judoka is designated by what is known as the - ranking system. This system was developed by Jigoro Kano and was based on the ranking system in the board game Go. Beginning students progress through kyu grades towards dan grades. A judoka's position within the kyu-dan ranking system is displayed by the color of their belt. Beginning students typically wear a white belt, progressing through