Spread the popcorn and pretzels together in a single layer across a large baking sheet lined with parchment.

Melt the white chocolate chips in a microwave-safe bowl in 30 second bursts, stirring between each, until smooth.

Stir in green food coloring a drop at a time until the chocolate is a bright, even green, white chocolate can seize if the coloring is added too fast.

Drizzle half the green chocolate over the popcorn mixture, then toss gently with a rubber spatula to coat.

Drizzle the remaining chocolate over the top and toss again, until most pieces show at least some green.

Scatter the red and green candies over the top while the chocolate is still wet, so they stick in place.

Let the mix sit at room temperature for 10 to 15 minutes, until the chocolate is fully set and no longer glossy.

Break into clusters and pile into a large bowl to serve.