Nun's Period Riddle

Alright, listen up, you big ol' dum-dum! You know the classic riddle, 'What's black and white and read all over?' The answer is usually a newspaper, 'cause it's black and white print, and people 'read' it. But THIS joke, oh man, it tricks your tiny brain! It changes 'read' to 'red,' like the color! And then it hits you with a nun, who wears black and white, and then... 'on her period.' Get it? Red blood! It's crude, it's a bit shocking, and it plays on a visual twist. You probably just thought of a newspaper, didn't you, you predictable bear cub?