Place 16 clear plastic shot glasses (or 3 oz plastic cups) on a sheet pan or in a baking dish.
Prepare the purple Jello layer. Boil 1 cup water in a medium saucepan. Remove from heat and then whisk the grape Jello powder into the hot water. Stir until the gelatin is completely dissolved.
Add 1/2 cup vodka and 1/2 cup cold water to the purple Jello mixture. Stir until well combined.
Pour the purple Jello evenly between each cup in a thin layer. Keep in mind that there will be six layers total so be sure to leave enough room. Move the cups to the refrigerator to allow the first layer to chill for 1.5 hours.
After the purple layer has set, prepare the blue layer. Boil 1 cup of water in a medium saucepan. Remove from heat and whisk in the berry blue Jello packet, stirring until completely dissolved.
Add ½ cup vodka and 1/2 cup cold water into the blue Jello mixture. Stir until well combined.
Pour Jello evenly between each cup in a thin layer, then move the cups back to the refrigerator to chill for another 1.5 hours.
Repeat this same process for the green, yellow, orange, and red Jello layers (in that order). After adding the final layer, move the cups to the refrigerator to chill for 1.5 hours, one last time.
Before serving, cut 2 rainbow berry Airhead strips into 1-inch pieces.
Add cool whip to a piping bag with a frosting tip, and pipe onto the Jello shots.
Finish them off by topping each Jello shot with an airhead strip. Serve and enjoy!