https://en.wikipedia.org/wiki/List_of_common_misconceptions#Sports
>The black belt in martial arts does not necessarily indicate expert level or mastery. It was introduced for judo in the 1880s to indicate competency of all of the basic techniques of the sport. Promotion beyond black belt varies among different martial arts. In judo and some other Asian martial arts, holders of higher ranks are awarded belts with alternating red and white panels, and the highest ranks with solid red belts.
It's not the colour of the belt that matters, but the size of the guy.