Place shot glasses at an angle in a muffin pan. Begin by spooning a couple teaspoons of red gelatin into each glass. Place in refrigerator and allow to partially set, about 20 minutes (it should no longer be liquid, and you should be able to lightly touch the surface with your finger). Next, add a little of the white gelatin to each glass. Replace in fridge until partially set, about 20 minutes. Repeat this process until you have the desired amount of layers. For the last layer you can sit the glass upright. Allow to set completely in fridge another 2-3 hours at least (or overnight).