Irish virginity test kit

Paddy is planning to marry and asks his doctor how he can tell if his bride - to - be is still a virgin.
The doc says," Aye Paddy, all Irish use 3 things for what we call a DIY virginity test kit.. A small can of red paint, a small can of blue paint and a hammer."
Paddy asks, " Aye and what do I do with these things Doctor ? "
Doctor replies, " Well before you get into bed on your wedding night, paint one of your balls red and paint the other one blue."........... If she says, " That's the strangest pair of balls I have ever seen " ................ " Then you hit her in the head with the hammer!"