Pour 1/2 oz grenadine in the bottom of the shot glass
Place the shot glass in the freezer for several minutes
Use a (clean) medicine syringe and slowly put/float the peach schnapps on top of the grenadine
Clean the syringe
Use the syringe to slowly put/float the blue curacao on the peach schnapps
Say cheers, clink your shot glasses, and enjoy!
Notes
This was made by trial and error. Layering the different colors can be tricky. We tried floating the colors with the back of a spoon, but after some research, we discovered that using a syringe was the most effective way to layer the colors. I realize it sounds strange to do it this way, but it looked perfect.