I'm gonna paint my crack.

The story:

I was with my mom, who knows lots about the "Rolling Stones",I was unsure about what the lyric was. She asked me to sing the part that I wasn't sure about.
I sang it, and she told me that the lyric wasn't "gonna paint my crack", and that the real lyric was "want it painted black". That cleared up alot, because I didn't understand why anyone would wanna paint their ass!!