How can you tell if she is virgin or not?

Paddy was planning to get married and asked his doctor how he could tell if his bride is a virgin.

The doctor said, “Well, you need three things from a do it yourself shop. A can of red paint, a can of blue paint… and a shovel.”

Paddy asked, “And what do I do with these, doc?”

The doctor replied, “Before the wedding night, you paint one of your testicles red and the other one blue. If she says, ‘That’s the strangest pair of balls I ever saw.’, you hit her with the shovel.”