
Don't be upset if you guessed incorrectly. I did a test like this to Becky a month ago (covered up Cammy's birthmark with a bow) and she got it wrong.
The easiest way to tell them apart in this picture: hold up a spoonful of baby food to your monitor. Whichever one breaks through the screen and eats it is Cammy and whichever one turns her head and frowns is Riley.