This item is easy to do and will baffle just about anyone.

The magician shows a shell and opens it up. Inside is an image of a white pearl in the center of the shell. The white pearl has a clear cover so one can not touch it. However, when the magician covers the pearl, the pearl becomes red! Covered again, it becomes blue. The pearl gets covered one more time and changes to a gold color. The shell can now be passed out for examination.