Martial Arts Belts
It's said that in ancient times, practitioners of martial arts had only one color belt (a.k.a. obi) - white. As they trained over the years it would become stained with dirt, sweat and blood, turning dingy brown then eventually black, so you would know that a person with a black belt was exceptionally skilled in their art.
This is a very nice story but it's completely made up and completely modern. In the really ancient times, your martial prowess was demonstrated by being skilled enough to live to old age. In Japan, where the belt system originated, the various schools of martial training (which included samurai swordsmanship and other weapons as well as unarmed combat) did have ranks, but they were denoted with certificates and secret literature detailing the techniques of the school.
Colored belts to denote rank in martial arts are a relatively modern invention, out of the post-Samuri Meiji Era of Japanese history. In the 1880s, the founder of Judo, Kano Jigoro, began using white and black obi to denote novices and experienced practitioners respectively. After the modern martial arts uniform, the gi, was developed in the early 1900s, colored belts were added corresponding to numbered kyu ranks, with a black belt signifying dan ranks. (Some sources say that the intermediate colors originated in Europe first, not in Japan; another source says the first to use colors was Brazilian jujitsu.)
The number, colors and significance of the belts varies greatly between martial arts, and even from dojo to dojo. There are some consistent similarities: White is always the beginner's color, either the lowest kyu or lacking a rank; a few schools still use white belts for all kyu. Black is nearly always dan rank and is usually the highest belted rank; successive dan ranks are either simply numbered or indicated by adding stripes or other marks to the belt. The order of colors in between varies, but one theory is that early on, instead of receiving a new belt, the older ones were dyed to their new color, so they had to go from light to dark in order for successive colors to show up. A few Korean martial arts such as tang soo do and soo bahk do replace black with "midnight blue" for philosophical reasons: black is associated with death and signifies the end of the journey, which dan rank is not.
In some organizations, children will have a different rank structure than adults, with more levels and or intermediate stages to go through, reflecting their natural inexperience. Sometimes this means more kyu ranks, sometimes this means "half-ranks" denoted by a stripe on whatever belt they're on. They may also restrict black belt ranks to those above a certain age, i.e. 16, or have a "junior black belt" that is counted separately from a full black belt.
The meaning of the black belt itself varies. The perceived meaning to western minds is that the black belt indicates mastery. However a first dan black belt is still a student (who may be addressed as sempai). They will generally assist the sensei in classes and may begin to teach in some capacity, but generally won't be acknowledged as a full sensei for a couple more dan ranks. (The Other Wiki gives the analogy as a first dan black belt being like a bachelors degree - fluent in all the basics but lacking the experience that breeds full mastery). The highest dan ranks in a school are usually reserved for those who not only show mastery in the art but also contribute back to it as an instructor and/or leader, and past 5th dan or so are awarded solely by the will of the organizational body. For normal rankings, some schools award ranks based on completing a test demonstrating your skills, some grant ranks whenever the Sensei decides they've earned it, and some award them based on the amount of time you have been training. Aspiring black belts should beware what the martial arts community derisively calls the "McDojo" - schools that are operated as a business (not bad in and of itself) and promise black belts in an unrealistically short amount of time (definitely bad). For an adult without prior martial arts experience, three to six years is considered the average time to go from white to black. (There are a few exceptions but such programs tend to be run by police or military organizations and are extremely intensive.)
There is also a stereotype that a person with a black belt can kill with his or her bare hands. This is a gross oversimplification, if not patently false. Let's face it: it's easy to kill people. If you get someone to stand still long enough, you can kill them with your bare hands or a spoon or even a pillow. What's difficult is having the physical and mental training to avoid hurting someone, to pull back and demonstrate that not only could you have handed out a Curb Stomp Battle, but you have chosen not to. In this sense, a black belt demonstrates not your skill with your fists, but your Character Development from Arrogant Kung Fu Guy to Martial Pacifist.
In some schools there are also a few belts higher than black, though they are rarely seen. In Judo, 6th through 8th dan are given a wider belt, red with a white stripe, while 9th and 10th dan have a red belt. Kano Jigoro believed that if ever anyone passed 10th dan, they've transcended the need for colors and grades and return to a white belt. (Kano himself, as the founder, has the honorary rank of 12th dan.) In other schools, the red belt is reserved for the school founder or current Grand Master. There is some controversy involving red belts, by the fact that in theory anyone can (and in truth, a few people have) declare their martial arts to be a "new style", found their own school and declare themselves 10th dan Grandmaster in it - some deserve the honor and some don't.
Other similar uses of clothing to denote progressive rank are lumped in here too - martial arts out of China, for example, are more likely to use colored silk sashes.
Many seasoned martial artists will tell you that the art isn't about gaining rank, it's about the journey. Belts fill the desire to have tangible marks of successful progress along the path, but if you give them too much importance, you're missing the point.
Variations in various martial arts
- Some schools of Aikido use only white and black belts, or white, brown and black. Aikido practitioners may also wear hakama: in many schools this is a privilege earned by higher rank students.
- Brazilian Jujitsu has belts that go white, blue, purple, brown, black, red and black and red, with ranks in between marked by stripes. Students move up in rank much more slowly, with average time to black belt being around 10 years; it is, therefore, much more accurate to associate black belt with mastery.
- Contemporary Capoeira adopted a belt system inspired by the oriental arts in order to cultivate image as legitimate sport so that they could get funding from the government. Belts are almost always braided cords of various bright colors with gray generally being the beginner cord, white being the master level (because you're supposed to be good enough to avoid dragging your cord and pants through the dirt). They frequently use the colors ofthe Brazilian flag (green, yellow, blue and white, and various combinations thereof)) with higher rank being denoted by colors closer to the center. However, various groups use a wide variety of different rope color progressions; the only common value is that white is always a master's belt.
- Kendo has kyu and dan rankings but no belt system.
- Muay Thai has something called a Pra Jiad, an armband worn around the upper arm, traditionally to bring confidence and luck. Some schools use colour variation on these, though the meaning varies - sometimes it means the student has taken some number of gradings, sometimes a number of wins in the ring, and an instructor might wear one signifying that he's trained a fighter from scratch to his first ring win.