Pour 1/3 cup of the red Jello mixture into each jar. Place the jars in the refrigerator to chill for around 40 minutes, until the mixture has begun to set and is no longer liquid.

While the red Jello is chilling, prepare the white layer. Whisk together two packets of unflavored gelatin with one cup boiling water and the sweetened condensed milk. Continue stirring until all the gelatin has been dissolved. Allow the mixture to sit at room temperature to cool until the red Jello is set.

When the red Jello is set, carefully pour 1/3 cup of the white gelatin mixture over the top of the red. Return the jars to the refrigerator to chill for around 20 minutes, until the white layer is set.

While the white gelatin is setting, prepare the blue layer by whisking together the berry blue Jello, one packet of unflavored gelatin, and 2 cups boiling water. Continue stirring until all the gelatin has been dissolved in the water. Allow the mixture to sit at room temperature to cool until the white gelatin is set.

When the white gelatin is set, carefully pour 1/3 cup of the blue Jello over the top of the white layer. Return the jars to the refrigerator to chill for an additional 3 hours.

Top your red white blue jello parfait with whipped cream and sprinkles, if desired, before serving.