Students should always remember that gradings are a privilege, not a right. Just because you have been a member of a dojo for some time and are friends with the senior students, and so on, does not give you the right to do gradings when you please. The privilege to participate in a grading for any level is earned through dedicated regular attendance and determined training. The instructor has the last say as to whether you may participate in a grading or not. Do not take it for granted. No one is that good. One of the worst practices one can adopt is simply to turn up for training a few weeks before a grading to sharpen up a little, and then expect the grading to just fall into your hands. It is just not that easy. Certainly some students may be able to do this, but talent does not justify disregard for common courtesy. Such an attitude demonstrates a very fundamental misunderstanding of the grading system. It is common courtesy to the instructor and to one's fellow students, to participate in the activities of the dojo in a spirit of friendship and humility. In this way the dojo grows stronger and one's personality is broadened. Of course if one is genuinely unable to attend at training more than once or twice a week then that is a different story. Such a situation should be discussed with the instructor. From experience though most instructors will be able to tell you that genuine reasons for failure to attend class to take training are very few and far between.
Karate Belt
Karate belts were first introduced in the art of Japanese Judo. This "colored belt system" was then adopted by karate, and was used first by Sensei Gichin Funakoshi and Shotokan Karate. They would say that if you work hard enough, the belt would change colors and show how much work you've done. That is why you never wash a karate belt. But most say that the belts were just "dyed" every time you would advance.
The Karate belt system is used in martial arts training to show the progress that a student has made in his/her study. The student starts out at a low rank of belt and progresses through the ranks to make it to the top to instruct students him/her self. They have to advance through the ranks (called kyu) to show their honor. To advance belts, they must show that they are ready for it by doing a belt examination