Preheat the oven to 375 degrees and lightly spray a baking sheet with cooking spray or line it with parchment paper.
Roll out the pizza dough until flat, then use a round cookie cutter or a bowl slightly larger than your cutters to cut ten circles; re-roll any scrap dough as needed.
Spread a thin layer of pizza sauce onto each dough circle and add mini pepperoni if desired.
Bake the sauced dough for 10 minutes, or until the edges have just started to brown; do not add cheese yet.
While the dough bakes, use cookie cutters to cut Halloween shapes from the mozzarella and Colby cheese slices.
Remove the mini pizzas from the oven and place the cheese cutouts onto each pizza, then add black olives as eyes if desired.
Return the pizzas to the oven and bake for about 2 minutes, until the cheese has just melted.