Pour 1 cup of water into a small saucepan and pour 2 packets of unflavored gelatin into the water. Warm the water and gelatin over a low heat, stirring occasionally, until all the gelatin has dissolved (about 5 minutes).
Remove pan from the heat and add 1/2 your can of condensed milk to the mixture. Stir until the ingredients combine.
Add 2/3 cup of vanilla vodka. Cover and set aside half of your milk mixture. You will need to use it for the last layer.
Evenly distribute the first half of your mixture into 20 disposable shot glasses, filling them about 1/3 full. Refrigerate until firm (30-40 minutes).
Each layer will take around 30 minutes to set. Be sure to wait until each one is fully set before adding the next.
When the first layer is firm, pour 1 cup of water into your saucepan and add another packet of gelatin to make your middle layer.
Warm the water until the gelatin dissolves, remove from the heat, and stir in the box of orange Jello until it dissolves. Then, add 1/3 cup vanilla vodka.Evenly distribute the orange layer on top of white layer and refrigerate until chilled.
Distribute your yellow layer on top of the orange layer and put it back into the fridge until it sets, for about 2 hours.
Notes
If one of the mixtures starts to set and you can't pour it into the shot glasses before, put it in the microwave until it warms up.