Line a rimmed baking sheet with a silicone liner or parchment paper.
Pop the popcorn kernels with an air popper. Remove any unpopped kernels and place the popcorn in a large bowl.
Combine the sugar, water, salt, butter, and vanilla in a heavy saucepan. Bring to a rolling boil over medium heat. Continue cooking for about 3 minutes, then stir in as much food coloring as desired.
Quickly drizzle the hot mixture over the popcorn, stirring with a silicone spatula. Stir until all the popcorn is evenly coated.
Spread the popcorn on the prepared pan and let sit at room temperature for at least an hour or until no longer sticky to the touch.
Notes
You will need about 6 tablespoons of popcorn kernels to equal 12 cups of popped popcorn.
For different flavors, use another extract or flavoring oil instead of vanilla.
Store candy popcorn in an airtight container for several days. (Just make sure it's completely set first.) Keep it away from humidity to preserve its crunchiness.