An ideal ending for a summer brunch.
In small saucepan, whisk sugar and 1/2 cup water over medium-high until sugar dissolves, about 2 minutes. Remove from heat. Stir in grapefruit juice; reserve 1/4 cup in small bowl. Pour remaining grapefruit juice into ice pop molds. Freeze until slushy, about 1 hour. Stir liqueur into reserved grapefruit juice; divide among molds. Using skewer, stir a few times to slightly blend the layers. Insert ice pop sticks. Freeze until solid, about 4 hours.