Legend has it there were only two original belt colors in martial arts.
You start with a white belt. Over time, your belt becomes dirty and turns black. Repeated experience is the only way to earn a black belt.
Think the black belt is the end of the line? When an expert continues his learning path, his belt fades back to the white fibers it’s made of.
When you feel like you’ve learned it all, the fibers of your belt will tell the truth.
If you want to spot the masters, look for the ones who are on a mission to remain open to learning more.