Line a baking sheet with parchment paper or a silicone mat to prevent sticking.
Place the white candy melts in a microwave-safe bowl. Microwave in 30-second bursts, stirring between each round, until completely melted and smooth.
Pour the melted white candy onto the lined baking sheet. Use a spatula to spread it into a smooth layer, about ¼ inch thick.
In separate bowls, microwave the orange, purple, green, and black candy melts using the same method; 30 seconds at a time, stirring until melted and smooth.
Spoon dollops of each colored melt over the white base. With a toothpick or skewer, swirl the colors together to create a marbled, festive design.
Quickly sprinkle on the candy corn, crushed pretzels, and Halloween sprinkles while the candy is still soft. Lightly press the toppings into the surface to help them adhere.
Leave the bark at room temperature for 1–2 hours to firm up, or place it in the fridge for about 30 minutes for a faster set.
Once hardened, break the bark into chunks by hand or cut it into pieces with a sharp knife.
Keep the finished Halloween bark in an airtight container at room temperature.
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