Here's a magic effect that gets even more magical throughout your performance! Audiences love it!
Show 4 separate black dice. Then, you show a quite empty cover and cover the dice. Then, you place a colorful puzzle with four different colors on the side of the cover. Remove the cover and, magically, all the black dice have changed to the colors of puzzle in the exact same order! Now you have some fun - replace the colorful cover, and move all the colors to the bottom, leaving only one color showing. When you again remove the cover, all the single-color dice have changed into to one die of that same color.
If that's not enough, there's more magic to come! Again, replace the cover and, with a black marker, make a drawing that divides the final remaining square into 4 pcs. When this cover is removed, the colored die has changed into 8 small colorful dice!