Four hearts - Red, Blue, Green and Black - are on the table along with a closed jewelry case. Tell the person the jewelry case contains a necklace with a heart hanging from it. Have the person pick a heart. An easy force method - explained in the instructions - will leave the person with a choice of Red or Blue. Before you open the jewelry case, ask the person if they would like to change their choice from Red to Blue or vice versa. When you have a final answer, open the case and show that indeed the color they chose is the color of the heart hanging on the necklace.
This is very easy. You can do it. Giving the audience the chance to change their mind in mid stream makes this trick even more amazing.
There is also the opportunity to come up with a story about where the jewelry box came from, where it's been, and the security measures taken to assure no one knows what the color is attached to the necklace."Before my birth, my mother put this closed jewelry box in a mayonnaise jar under Jerry Springer's back porch with instructions to do this trick for, and what are you names again?, yes, exactly. What luck.!"