How do I know if I'm an active player in Dance Central 2?

If the Kinect is tracking you as an active player, your skeleton will be highlighted in one of the shadow boxes in the upper left or right corner. If you're playing with a friend and are uncertain which one of you is the pink player and which is the blue player, have one person keep their hands down and the other player wave. The skeleton that waves with the player belongs to that player, as do the cards and dancer on that side of the screen!