In a small saucepan, bring blueberries and 1/4 cup sugar to a boil over high. Reduce heat and simmer, crushing berries against side of pan with a wooden spoon, until mixture is syrupy, 3 minutes. Transfer to a small bowl and refrigerate until cool, 30 minutes.

In a medium bowl, whisk together 1/2 cup sugar, yogurt, and cream until sugar dissolves, about 2 minutes. Pour yogurt and blueberry mixtures, alternating them, into eight 3-ounce ice-pop molds, making 5 or 6 layers in each. With a skewer or thin-bladed knife, swirl mixtures together in an up-and-down motion. Insert ice-pop sticks and freeze until solid, about 6 hours (or up to 2 weeks).