It's Done with Mirrors! Card Trick

A miracle in your hands!  4 Kings (or other 4 cards) are pull face up from the top to the bottom of their stack.  When you do it again, one has mysteriously turned face down!  This is repeated and a different one has turned down.  This continues until each one has turned face down one at a time and all back to face up.  The question is asked, "Now what color are the backs?"  They answer, "red".  You turn the cards over and say, "No, this is done with mirrors!"... all of the backs have changed to mirrors