I just got my first stripe as a white belt in Brazilian Jujitsu today!
I have no clue how many I need before I advance to a blue belt, but I'm guessing it's somewhere around 5 or 6.
At the end of class, the instructor called out two of us, and gave us each a white stripe.
Pretty ghetto - it's a stripe of athletic tape wrapped around the belt :)
The whole class applauded, and then as a celebration, the instructors took turns throwing us.
I'm very grateful that I know break falls... you probably can't get your first stripe without knowing break falls :p