The distinction of the level of each trainee is made by the color of the belt. In the old times in Korea, there were only two colors: white and black, representing the two states, Trainee and Instructor.
Now there are six colors; white, yellow, green, blue, red and black. The first five colors along with their two by two combinations are the first group of zones that result in the black one. After the black belt color does not change, but the level of skill changes, represented by the ranks 1st Dan, 2nd Dan etc. In the 4th Dan, according to Kukkiwon, the title of Assistant Instructor is awarded, in the 5th Dan the title of Instructor (Master), and in the 8th Dan the rank of Grand Instructor (Grand Master).