We will look at the order of the karate belt colours in this post. The order of the karate belts depends not only on the style of karate, but the individual karate school. Most schools have adopted a variation of the kyu ranking system.
I list below four of the most common belt order variations. These colours originated in judo, but have since found their way into karate styles such as Wado Ryu and Shotokan.
After the kyu grades are completed, the student will then work towards their first dan grade, i.e. their first black belt grade.
As you have probably noticed, each variation of the kyu belt ranking system is very similar. Colours are generally light to begin with and end up getting darker.
One possibility is the so called "Dirty Belt Theory" which theorises that belts start off as white but become blacker as they collect dirt and sweat. Most people cite lack of evidence for this claim.
Another theory is that in Japan during World War 2 it was cheaper to dye a belt than buy a new one. Anyone who has tried to dye clothing knows that you cannot dye dark colours light.
Most likely to make money. Their reasoning is that the more belts they have, the more money they can make from gradings. Often the additional belts come in the form of a colour with a white horizontal stripe through the middle, or a colour with a different colour horizontal stripe or even by adding a white vertical stripe on the end of a coloured belt. Be wary of such tactics.
Sometimes. Some styles use a red belt to denote a low grade, but there are some that use it for the belt right before black and others that only let the Grandmaster of that style wear it. Other schools choose to omit the red belt entirely. An alternately red and white belt is sometimes used to indicate that the wearer is a Master.