The colors of karate belts

Japanese Judo was the first martial art to introduce the colored belt ranking system as a visible indication of the students’ progress. The colored belt ranking system soon was adapted for Karate...

In the old days the white belt was simply dyed to a new color. This repeated dying process dictates the type of belt color and the order of the colors!. The standard belt color system is white, yellow, green, brown, and black. In some Karate school and styles, the color order is white, yellow, orange, green, blue, brown, black.

Due to the dying process, it is practical to increasingly use darker colors. All of this came about shortly after the second world war, when Japan was a very poor country, and dying the belts to a new color was a cheap way to have a visible, simple and effective ranking system...

Another explanation for the colored belts, that appears more like a Karate myth than reality, is the notion that the belts simply went from white to black because the original Karate founders never washed their belts. They started off with white belts and after years of training ended up with black belts...

Many people argue that this theory is cute but has little truth. The dirtiest belt will never go black, and although the color change from white to yellow to brown can easily be imagined, other colors like green would be harder to achieve...

There is also real evidence FOR this theory. Many Karate dojos in Japan have a change room where students are able to leave their Gi ready for when they return to train again.... After all, an old and dirty Gi must mean that its owner has used it a lot, and thus must be highly skilled. In that sense, the yellow/brown Gi functions exactly like a colored belt! 

Via Reddit, where there is a discussion thread