Why is belly button fluff always a light purple colour ;-)?
Aha, I actually know this one. Belly button fluff are pieces of lint traveling up your happy trail, like a conveyor belt, into your belly button. The lint/fluff rubs off your underwear through normal activities and slowly works it’s way up and up and up until it’s deposited into your belly button. Disgustingly enough, often the conveyor belt works in reverse and you get multicolored fluff in your derriere as well. It sounds like you either wear light purple underwear or multicolored underwear. Either way, the only way to reduce it is a) shave everything from the belly button down; b) go commando or c) wear tighty-whities. Those will only reduce it, not stop it completely. Have fun discovering other oddities about your body!
