ADD 2/3 cup boiling water to grape flavor gelatin mix; stir 2 min. until completely dissolved. Pour into 8x4-inch loaf pan sprayed with cooking spray. Refrigerate 1 hour or until firm.
ADD remaining 2/3 cup boiling water to berry blue flavor gelatin mix in medium bowl; stir 2 min. until completely dissolved. Add enough ice to cold water to measure 1 cup. Stir into blue gelatin until ice is dissolved and gelatin is slightly thickened; whisk in yogurt. Refrigerate 10 min.
UNMOLD grape gelatin; cut into 1/2-inch cubes. Add to blue gelatin; stir gently until blended.
SPOON into 8 (5-oz.) paper cups. Insert wooden pop stick into center of each. Freeze 4 hours or until firm. Peel off cups before serving.