In a blender, combine frozen strawberries, 2 cups of orange juice and 1/2 cup of confectioners' sugar. Cover and process until smooth; set aside. Rinse the blender container. Add blueberries and remaining juice and sugar. Cover and blend until smooth. Alternate layers of strawberry and blueberry in glasses; stir layers a few times to create a swirl. For garnish, thread a strawberry top, hulled side first, an orange slice and a strawberry tip, cut side first, through a drinking straw or stirring stick; place in glass.