Process watermelon, 1 teaspoon sugar, 2 tablespoons yogurt, 1 teaspoon juice, and 1 dash salt in a blender until smooth. Pour into a pitcher; rinse blender. Repeat with honeydew; the same amounts of sugar, yogurt, juice, and salt; and a separate pitcher. Repeat with cantaloupe; remaining sugar, yogurt, juice, and salt; and a third pitcher.
Fill bottom third of 16 ice-pop molds with watermelon mixture. Freeze 2 hours or until solid. Fill middle third of molds with honeydew mixture. Freeze 1 hour or until surface is frozen. Insert craft sticks in molds through honeydew layer; freeze 1 hour or until solid. Fill top third with cantaloupe mixture. Freeze until solid.