FWIW, he colored belts were really introduced for children
(actually, that was a large part of the reason for the whole ranking system in the first place).
While I realize they were introduced for children, and I completely understand the reason why they were designed for children, I have to say that I honestly think they are a good idea. I have to say from personal experience that while I have always been dedicated and focused in classes, and since I started at a new dojo, I was sempai, even with very little experience, but the belt makes a difference. Having a visible rank shows other students, particularly brand new ones, that you have the ability to teach them. Rank forces you to be better, simply because of higher levels of expectations of those around you. Personally, I felt a greater responsibility not to let down the other students, as well as to my Sensei, to show him that his trust and faith in me was not unjustified. While it sounds stupid, even to me, my techniques have gotten substantially better after I tested. I am much better at slowing down and being more deliberate and methodical, and that ability to slow down and relax has made vast improvements in my technique. I really honestly directly attribute this to the visible reminder that I have got to be better because I have rank now.
Just my .02... I'm sure I'm nuts though.