Blend watermelon and sugar in processor until smooth. Strain puree into bowl,pressing solids to extract as much fruit as possible.
2Place cups in shallow baking pan. Spoon watermelon puree into cups, dividing equally (scant 3 tbsp each). Freeze until mixture is almost frozen, about 2 hours. Cover cups with rounds of foil, sealing tightly at edges. Using tip of small knife, make 1/4 inch slit in center of each foil cover. Push ice pop stick through slit and securely into watermelon ice without hitting the bottom of cup. Freeze until watermelon ice is solid, about 1 hour longer.
3For Lemon Ice:
Bring 1/2 cup water and sugar to boil in heavy small saucepan over medium high heat, stirring until sugar dissolves. Remove from heat. Mix in lemon juice, orange juice, and vanilla. Cool to room temp.
4Place pan with frozen pops on work surface;carefully fold back foil over each cup without dislodging stick. Spoon lemonade into cups, dividing equally (scant 3 tbsp each) Reseal foil. Freeze until lemonade layer is solid, about 2 hours.
5For Blueberry Ice:
Stir blueberries, 1 cup water,sugar in heavy medium saucepan over medium-high heat until sugar dissolves. Boil until berries are very soft stirring occasionally, about 5 minutes. Strain mixture into small bowl, pressing on solids to extract as much fruit as possible. Mix in lemon juice. Cool to room temp.
6Place pan with frozen pops on work surface; carefully fold back foil over each cup without dislodging stick. Spoon blueberry mixture into cups, dividing equally (generous 3 tbsp each) Reseal foil. Freeze until pops are frozen solid, about 8 hours. (Can be made 2 days ahead. keep frozen)
7Remove foil, then tear or use scissors to cut cup off each pop; return ice pops to pan and freeze until ready to serve.