Belt history

Black belts were not worn as symbols of Judo dan grade until about 1886. However, these belts were not the same as belts worn today. Since Kano had not yet invented the Judo uniform, Judo students practiced in a "kimono" (the traditional Japanese robe) and wore the wide belt that is still worn with the formal kimono. In 1907, Kano introduced the modern Judo uniform and belt, but he still only used white and black belts.  

Gradually, colored belts were used to differentiate the kyu ranks. In Japan, white belts are generally worn through all kyu grades, although some schools also use the brown belt to indicate the higher kyu ranks. The blue, yellow, orange, green, and purple colored belts used by intermediate kyu grades originated in Europe and were imported into the U.S. system during the early 1950s. 

Black belts are traditionally worn by the technical ranks, first dan (shodan) through fifth dan (godan). A red-white sectioned belt is worn by the ranks awarded for service to Judo, sixth dan (ryokudan) through eight dan (hachidan. Solid red belts are used for ninth dan (kudan) and tenth dan (judan).