Line a baking sheet with parchment paper or a silicone baking mat.

In a microwave-safe bowl, melt the white candy melts in 30-second intervals, stirring well after each interval until smooth and fully melted.

Pour the melted white candy onto the prepared baking sheet and spread it into an even layer using a spatula. Aim for about 1/4 inch thickness.

In separate microwave-safe bowls, melt the orange, purple, green, and black candy melts in 30-second intervals, stirring well after each interval until smooth and fully melted.

Drop spoonfuls of each color of melted candy melts onto the white candy layer. Use a toothpick or skewer to swirl the colors together, creating a marbled effect.

Immediately sprinkle the candy corns, broken pretzels, and Halloween-themed sprinkles over the swirled candy. Press the toppings gently into the candy to ensure they stick.

Allow the bark to set at room temperature for about 1-2 hours, or place it in the refrigerator for quicker setting (about 30 minutes).

Once fully set, break the bark into pieces using your hands or a knife.