I was updating my book tentatively titled, The Science Behind All Fighting Techniques, and was looking into what a black belt originally meant when introduced by Jigoro Kano, founder of Kodokan Judo.
Kano introduced the black belt to distinguish between seasoned practitioners and others. Kawaishi introduced coloured belts for kyu grade because he was teaching in France and considered that Westerners needed some form or recognition for advancement.
So where did the colours come from for the kyu grades.
The International Judo Federation website refers to one theory that they were based on the colour of ... snooker balls. :) I just love this. Different colours with different values.
I've read a description for Kyokushin karate which refers to the colours of their kyu belts reflecting those of our 'aura.' The invisible energy fields that surrounds all living things apparently, although not so invisible if they formed the basis for a coloured belt grading system.
The martial arts (as opposed to the martial way) was developed by practical people for practical reasons. I just hate how it has be subverted and devalued by those who use it take people on a supposed 'magical mystery tour.'
If you want the whole analogy thing, which is the most important ball on the snooker table :) ... the white ball pots the coloured balls to win the game, including the black.