In most modern martial art discipline rankings I'm aware of, white belt is your rank when you step on the mat with no experience, so you don't really "earn" it. I think the metaphor would be whatever color the rank above white is, but that varies widely across disciplines.
But now I'm searching the comments wondering why the titles don't match.
To someone who doesn't do martial arts, white belt means something to me (inexperienced), as does black belt, all other colours are unknown points in between.
In conclusion. The HN crowd are pedantic and argumentative, so stay away from metaphors. :)
You usually have to cut your nails and buy a uniform, but yes - I found this headline confusing too. "Yellow belt" is pretty standard, but not universally so. BJJ goes straight to blue, but after much longer than Karate/Judo takes to get to yellow. The most prolific borrower of martial arts terminology in tech, the "six sigma" folks, call their second level "yellow belt" too.
