I can;t really say that it's a rank or color, I think students get bored, feel unchallenged, get discouraged, or think this is simply not for me, especially women when it comes to sparring. It seems sometimes like the color purple, you either hate it or you are passionate about it. Passion =life . It is what makes you a martial artist, we are not all Bruce Lee but the ones who stay or keep coming back, possess tamashi, indomitable spirit.