Place 4 small plastic shot glasses onto a flat tray.
Place the leaf gelatin into a small bowl and pour over cold water. Leave for around 5 minutes, until the gelatin has soaked up the water.
Squeeze the leaf gelatin until most of the water has dripped out and add it into a small dish with the condensed milk.
Stir the almost-dissolved gelatin with the condensed milk until the gelatin totally breaks down. If the mixture is still lumpy, try microwaving it for 10 seconds at a time until the gelatin dissolves.
Evenly divide the gelatin-condensed milk mixture between three small bowls.
Stir the vodka into the first bowl, the triple sec into the second bowl and the limoncello into the third bowl.
Stir a few drops of orange food colouring into the triple sec bowl.
Stir a few drops of yellow food colouring into the limoncello bowl.
Pour the white gelatin mixture evenly into the four shots and pop in the fridge for 15 minutes to set.
Remove from the fridge and pour over the orange gelatin mixture. Return to the fridge for 15 minutes to set.
Remove from the fridge and pour over the yellow gelatin mixture. Cover the shots and leave in the fridge until you're ready to serve.
Notes
This recipe makes just 4 small shots, but you can easily increase it to make as many shots as you want.