As if different colored belts weren't enough, nowadays you have to worry about the color of your uniform too. It can be confusing and a real hassle.
To figure out which gi color is right for you, the first stop you have to make is at your dojo/dojang. Various styles of martial arts have differing rules and opinions about which color can be worn and when. But if you are a little curious about the background of these colors, read on.
It's no accident that white is the most common color of gi found not just at karatedepot.com, but pretty much everywhere. White is the classic color you see in most traditional arts and is widely available. This came about from purely practical circumstances.
The cotton which was originally used to create these articles of clothing was white. Although it's doubtful the uniforms of yesteryear came as perfectly bleached and ironed as we get ours nowadays, the off-white of cotton fiber was easy and abundant. Once the habit of wearing white took hold, the strength of tradition ensured that it would be worn from then on.
Black gi developed later and are sometimes reserved for practitioners who have achieved black belt or above. The thought process being that new students could easily distinguish skillful students of a school who might help and teach them via the black gi and black belt. Of course there is also a strong possibility that black uniforms came along simply as an element of growing fashion in the arts.
Blue uniforms are an interesting story, and get their start in the world of judo. In 1997 the International Judo Federation instituted the wearing of blue gi and white gi to better distinguish players during competition. Blue is now available in other arts such as karate, but rarely holds the same significance and general acceptance as it does in judo.
Blue/indigo is also a common color in Kendo and Aikido in the form of Keikogi and Hakama. This is a long standing tradition, especially in swordsmanship, and does not necessarily denote rank of any variety.
Red gi appeared some time later with little explanation or fanfare. It seemed like a natural extension of the growing martial art fashion landscape, although it has no basis in tradition. Any other color combination you see is an extremely modern development and is used at the discretion of the school owner.
Generally speaking, you won't see much beyond standard white and sometimes black in traditional karate schools. Taekwondo has adopted a white gi occasionally with colored lapels, and MMA has taken to a variety of colors and patches as well as simple board shorts.