found this interesting
If you train at Kron's gym you don't get to wear your belt, they give you some other belt.
If you show up at Kron Gracie’s school, and you haven’t earned your belt from either him or his father Rickson, you have to wear a belt with a white running up the middle of it.
Recently, BJJ black belt Brian Anthony Mendez posted a picture of himself at Kron’s Academy. When asked why his belt had a lengthwise white strip going up it, Anthony explained that he had to wear one at Kron’s school:

At Krons school if you show up there and you didn’t get your rank from Kron or Rickson Gracie you have to where stripe on your belt
Shortly after, one of Kron’s brown belts explained the reasoning behind the rule.

