In the martial arts world, colored belts are used to signify rank. However, this ranking system is different and specific to each different practice and school. A black belt in karate does not translate to a black belt in Tae Kwon Do. When the belt was first used as a ranking system, martial artists would start with a white belt and dye it darker and darker as they progressed and advanced to the next level. Once earned, they would eventually dye their once white belt to black which signifies the highest rank in martial arts. In current times, various colors of belts are used to signify rank. The levels are typically defined by lightest belt as the lowest rank to the darkest which signifies the highest rank. You must keep in mind that each school has different criteria in which a martial arts can earn the next rank of belt. The color of the belt can be used as a guideline to judge what level or rank a practitioner has reached.