The magician opens a black box and takes out a solid black cube which is plain on all sides. With a wave of his hand, the magician causes a white clock face to appear on one side of the black cube. Then the cube is placed back in the box and the lid is placed on top. 

Another magical wave, and the box is opened, and the cube removed to show that white clock faces are now on all six sides! Once again, the cube is placed back in the box and the lid is placed on it. 

For the finale, the box is opened one last time and, now, when the cube falls out, it has a clock face on all six sides and each clock face is a different color! Looks great!! Your audience will be stunned!