What are the differences in the colour of collars of Tae Kwon Do dobok?

The purpose and meaning of different color of collars on Taekwondo dobok (uniforms) will vary depending on the school, Kwan (family of schools), or organization.

For the most basic difference, according to the standards of the Kukkiwon (World Taekwondo Headquarters in Seoul, Korea), the dobok (도복) should be all white for geup students (color belt grades), and a black collar for all Black Belts 1st Dan and above. The half red/half black collar and belt are used for the student who reaches the Black Belt level while under the age of 15. Only an adult, 15 and older is considered a "Dan" (pronounced "dahn" or "Don"), and Junior Black Belt is called a Poom. There are four levels of the Poom that may be transferred to Dan when appropriate age is reached.

In some organizations outside of Korea, Black Belts retain the white collar, and the black collar trim is only used for a school owner, or chief instructor. Prior to that, Assistant instructors might have black trim around the base of the jacket, or thin red trim around the collar. In many Taekwondo organizations, a stripe down the pant leg is worn only by a Master (often 4th Dan or higher).

Since uniforms of a wide variety of color and trim can be ordered by school owners from numerous available suppliers, independent schools and instructors might elect to use colored collar trim at any stage, including colors matching the belt color at the geup level (e.g.: yellow, green, purple, blue, etc.).