How can I set a property associated with a Control onClick when the subroutine is used by multiple Controls?

I have several PictureBox controls that all call the same subroutine on a CLICK event.  The Delegate subroutine looks like this: (where sender is the PictureBox control that was clicked.

private void AnyPicture_Click(object sender, EventArgs e) {}

How acheive sender.BackColor = Color.Red when any of several PictureBox controls could have raised this CLICK event?