Line a large baking sheet with wax paper.
With a 2-inch round cookie cutter, cut 18 circles from your graham crackers.
Add a dollop of marshmallow fluff about the size of a grape to the center of half your graham circles. Top them with the remaining circles to make graham and marshmallow "sandwiches."
Divide your almond bark evenly between three microwave safe containers.
Heat your first container of almond bark according to package instructions and stir until smooth. Stir in your orange food coloring (do NOT add more than 3 drops, since adding too much liquid can cause the bark to seize up). With a small rubber spatula or plastic utensil, lower one of the graham sandwiches into the melted bark. Swirl the bark over and around it until it's completely covered. Gently slide the utensil under the moon pie and lift it out of the bark, transferring it to the baking sheet. Repeat this step for 2 more graham sandwiches. Using a few dots of extra orange almond bark as glue, fix a piece of green gumdrop to the side of each orange pie (the green gumdrop will be the stem of your pumpkin). Allow them to completely harden (about 20 minutes).
While you wait, heat your second container of almond bark and stir until smooth. Stir in your purple food coloring. Lower a graham sandwich into the container and completely coat it with purple bark. Remove it to the baking sheet using your utensil and repeat this step for 2 more pies. Gently press your icing decorations into the surface of the purple pies, just enough to make them adhere.
Heat your third container and stir until smooth. Completely coat your last 3 graham sandwiches one at a time and remove them to the baking sheet. While the bark is still warm, use your tube of black icing to draw a tight spiral onto the surface of each one. Use a toothpick to draw 6 straight lines radiating out from the center of the spiral, turning them into spider webs.
When your orange pies are completely cooled, use your black icing to draw a jack o' lantern face on the surface of each one.