When a limp penis is inside an ass or vagina and then gets erect with such girth that is causes bruising to legs, thighs and ass resembling purple shorts
I just gave that girl purple shorts.
When someone takes your pants, and like guillotines them before taking a sharpee and purpling all that's left over.
Robespierre: Off with his pants!
Random ah dude: Aye, aye, sir!
Robespierre: Now sharpee him!
*Random dude then colors in with purple sharpee to give him purple shorts*