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.
karate belt colors
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.
The dying of the belts became part of the Karate tradition and was also adapted in other countries. In Australia, Sensei Terry Lyon of Lyon-Karate.com reports that in the early 70s, Australian Karate students also dyed their belts to their new color.
http://www.all-karate.com/125/history-of-karate-belt-colors
that link also talks about Bagardbilla’s response and how that might have little truth to it.
Karate belts
Can vary between the different types of karate( Shito Ryu, Wado Ryu, Goju Ryu, & Shotokan) The type of Karate that I am doing is Wado Ryu. The belts are:
-White belt (ungraded)(10th Kyu)(9th Kyu)
-Red belt (8th Kyu)
-Purple belt (7th Kyu)
-Green belt (6th Kyu)(5th Kyu)
- Brown belt (4th Kyu)(3rd Kyu)(2nd Kyu)
-Black belt (1st Kyu)
http://wiki.answers.com/Q/What_are_the_colors_of_Karate_belts_in_order_from_white_the_lowest_to_black_the_highest
looks like its all based on the style