I've often thought about adding blue and brown belts to our class ranking. But it's not really that important. It kind of makes students feel good, kind of helps new people judge who has a more informed opinion, but I also think colored belts are kind of silly.
I've been a member of dojos that did the colored belt thing and dojos that didn't. I understand awarding colored belts in kids classes but overall I tend to go with the KISS principle when possible and would prefer the white-until-black.