You should perhaps read up a little more. The myth is not that the white belts went through COLOR changes as they got dirtier....merely that they got ...

You should perhaps read up a little more. The myth is not that the white belts went through COLOR changes as they got dirtier….merely that they got dirtier and darker as it was tradition not to wash your belt or obi. The dirtier your belt got meant the more experience you must have in training….a very dirty belt would signify someone with many years experience. But the belts did not change colors like orange or green or become absolutely black. Now the colors go from lighter shades to darker as a representation of this and also most likely (as you mentioned) because a single belt could also be dyed gradually darker and darker colors.

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