Directions

1. Combine watermelon, lime juice, and corn syrup in a food processor or blender and process until very smooth. Pour mixture into a 1-cup glass measuring cup. Divide mixture evenly between 6 (2.5 fluid ounce) rocket-shaped ice pop molds (use about 1 tablespoon plus 1 teaspoon per mold). Freeze until the watermelon layer is firm, about 2 hours. Save any leftover mixture for other uses.
2. While the watermelon layer freezes, combine water, sugar, and lemon juice in a small saucepan. Bring to a boil and boil until the mixture reduces to 1/2 cup, 5 to 7 minutes. Let cool completely.
3. Remove pop molds from the freezer. Divide lemonade mixture evenly among the ice pop molds, pouring it on top of the watermelon layer. Tear 6 small sheets of heavy-duty aluminum foil and cover the tops of the molds. Using a paring knife, cut a small slit in the center of each aluminum foil cover and insert a wooden craft stick, making sure sticks are vertical. Freeze pops until the lemonade layer is firm, about 2 hours.
4. Combine blueberries, yogurt, and blue food coloring (if using) in a food processor or blender and process until very smooth. Strain the mixture through a fine-mesh wire strainer to remove berry skins. Remove foil from ice pops. Divide blueberry mixture evenly among the ice pop molds, pouring it on top of the lemonade layer. Cover with foil, return to freezer, and freeze until the blueberry layer is firm, about 2 hours.
5. To unmold the ice pops, fill a tall water glass with warm water. Submerge a mold in the water until the pop slides out easily, about 5 seconds (be careful not to submerge the pop so much that water gets into the ice pop). Repeat to unmold remaining pops. Ice pops keep, frozen, about 3 weeks.