Use food coloring to dye each ball of dough a different color of the rainbow. Start with red, and add 3-5 drops of food coloring to the middle of the ball and then use your hands to work the color though the the dough until it's distributed evenly. You may want to wear gloves to protect your hands from the food coloring, or mix the dough in your stand mixer, or food processor. Mix each color individually until they're all done. Add more or less food coloring to create lighter or more vibrant colors, whichever you prefer. You can use the primary colors to create a new color. To make orange add red and yellow. To make purple, mix red and blue together.
Prepare a lightly floured surface and break each colored dough ball in half. Arrange the balls of colored dough so that there's a good mix. Flatten them together first with your hands, and then use a rolling pin to roll them out into a large sheet, about ¼ inch thick.
Traditional pop tarts are 3 x 5 inches. Cut a 3 x 5 inch rectangle template from the pie crust box, or use a ruler and a knife or pizza cutter to cut out 6 rectangles.
Place 3 rectangles onto a prepared baking sheet sprayed with non-stick cooking spray, or lined with parchment paper.
Add about 1 tablespoon of jam to each rectangle, leaving about ½ inch around the edge with no jam. You can use any kind of jam you like for the filling.
Next, place another rectangle on top. Use a fork to go around and seal the edges so that none of the jam escapes. Bake the pop tarts at 350 degrees for about 10 minutes, until the edges are just turning golden brown. Let the pop tarts cool on a wire rack.
While they're cooling make your simple icing. Place the powdered sugar, milk and a splash of vanilla in a small bowl and stir to fully combine. When the pop tarts are fully cool, spread the icing on top of each one, and while the icing is wet, sprinkle with colorful sprinkles. Store in an airtight container at room temperature.
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Notes
Let your pop tarts fully cool before adding the icing. Be sure to add the sprinkles while the icing is still wet before it sets so that they will stick.Store any leftover pop tarts in an airtight container at room temperature.