1In a medium bowl, dissolve strawberry Jell-O in 1 cup boiling water. Stir for 2 minutes until completely dissolved. Add 1/2 cup cold water. Pour into a 9x13-inch dish. Refrigerate for 1–1.5 hours, or until slightly thickened.
2In a bowl, sprinkle unflavored gelatin over 1/2 cup cold water. Let sit for 5 minutes to bloom. Add 1 cup boiling water and stir until dissolved. Stir in condensed milk and vanilla. Fold in whipped topping until smooth. Pour gently over the red layer. Refrigerate for 1–1.5 hours, until set.
3In a medium bowl, dissolve berry blue Jell-O in 1 cup boiling water. Stir for 2 minutes until completely dissolved. Add 1/2 cup cold water. Let cool slightly. Pour gently over the white layer. Refrigerate for at least 4 hours, or until fully set.
4Top with whipped topping and red, white & blue sprinkles, if desired. Cut into squares and enjoy!