colour

I saw a lot of magicians doing the artwork prediction, when he choses some spectator to colour a draw of a person with wite clothes, and they have the prediction and even the same clothes that the person colored on the draw, someone knows how they do it??

Are there any nice colour changes that involve moving the top card of the deck to the bottom - with the bottom card being the one that changes? I know there is a basic one that is explained in The Royal Road, but after learning it, I question it's practicality.