Mix boiling water with lime Jell-O and mix until the gelatin is dissolved. Add cold water and mix to combine.
Pour half of the mixture evenly across small cups (about 8). Refrigerate for 1 hour.
Mix the remaining Jell-O mixture with the condensed milk (IMPORTANT – DO NOT REFRIGERATE)
Once the first layer of Jell-O is set, remove from the refrigerator.
Pour the Jell-O/milk mixture over the set green Jell-O mixture evenly across each of the cups.
It should make a separate lighter layer.
Refrigerate for at least 4 hours or overnight