Place the 6 12-ounce plastic cups onto a baking sheet so that you can easily move them back and forth to the refrigerator.
Blue Layer
Boil 2 cups of water and place into a medium bowl or 8-cup liquid measuring cup. Add the 3 oz. blue gelatin and stir to dissolve. Stir in 2 cups of cold water. Distribute 1/2 cup of the blue gelatin into each of the 8 plastic cups on the baking sheet. Place them into the refrigerator to chill for 2 - 2 1/2 hours until set.
White Layer
While the blue gelatin sets in the fridge, in a 4-cup measuring cup, mix 1 cup of boiling water with the 14 oz. sweetened condensed milk. Set aside.
In a small bowl, place 1/2 cup cold water and sprinkle 2 packets of the unflavored gelatin over the top. Let it stand for 2-3 minutes, until the gelatin looks grainy. Add 1/2 cup boiling water to the bowl and stir until gelatin dissolves completely. Pour this mixture into the condensed milk mixture and stir to combine. Set aside and let the contents come to room temperature. Pour 3 ounces of white gelatin into each of the 8 cups. Return to the refrigerator to chill for 1 hour or until set.
Red Layer
In a medium bowl, add 1 cup of boiling water to the cherry gelatin. mix to completely dissolve. Add 1 cup cold water to the bowl and mix well. Pour 1/2 cup of the cherry gelatin into 4 of the cups over the white gelatin layer. Place into the fridge to set for at least 4 hours before serving.
Green Layer
In a medium bowl, add 1 cup of boiling water to the lime gelatin. mix to completely dissolve. Add 1 cup cold water to the bowl and mix well. Pour 1/2 cup of the lime gelatin into the 4 remaining cups over the white gelatin layer. Place into the fridge to set for at least 4 hours before serving (I left them in overnight.)
Just before serving, top each of the cups with whipped cream. Sprinkle 4 of them with red, white and blue sprinkles and the other 4 cups with green sprinkles.
Notes
It may look like a lot of ingredients and steps, but this recipe really does come together quite easily.
If pressed for time, you can use the Speed-Set method as described on the gelatin packages that uses less water, but includes ice cubes.
Berry Blue: Dissolve the gelatin in 1 1/2 cups boiling water. Add enough ice to 1 cup of cold water to make 2 1/2 cups. Stir the ice water into the the blue gelatin and mix until slightly thickened. Remove any unmelted ice cubes. Pour 1/2 cup of gelatin into each of the 8 cups. Refrigerate for 30 - 90 minutes or until firm.
White Layer: I have no cold set directions for this layer, so follow as directed in recipe.
Cherry (red): Mix gelatin with 3/4 cup boiling water and dissolve. Add enough ice to 1/2 cup cold water to make 1 1/4 cups. Stir into the cherry gelatin and mix until slightly thickened. Remove the unmelted ice cubes. Pour 1/2 cup into 4 of the cups over the white layer. Refrigerate 30 - 90 minutes or until firm.
Lime (green): Mix gelatin with 3/4 cup boiling water and dissolve. Add enough ice to 1/2 cup cold water to make 1 1/4 cups. Stir into the lime gelatin and mix until slightly thickened. Remove the unmelted ice cubes. Pour 1/2 cup into the remaining 4 cups over the white layer. Refrigerate 30 - 90 minutes or until firm.
For 16 servings, use 9 ounce plastic cups distributing 2 ounces ( ¼ cup) of the blue layer, 1.5 ounces of white, and 2 ounces (¼ cup) of each of the red and green gelatins.
I found it easiest to mix all of the gelatins in my liquid measuring cups and then pour the exact amount needed for each dessert into a smaller measuring cup to transfer it.