Line a large baking sheet with a Silpat mat or parchment paper.
Pour the white chocolate chips into a large heat-proof bowl or the top of a double boiler. Pour the candy melts into smaller heat-proof bowls.
Bring two pots of water to a boil - one large and one small.
Place each bowl of the candy melts over the smaller pot, ensuring that the bowl does not touch the water. Melt, stirring often, until smooth. Set aside and repeat with the remaining bowls of candy melts. See notes below for how to melt the candy melts in the microwave.
Set the larger bowl of white chocolate chips over the larger pot, ensuring the bowl is just over the water and not touching it. Heat, stirring frequently, until smooth.
Using a silicone spatula or offset spatula, spread the melted white chocolate onto the prepared baking sheet, about 1/4-inch thick.
Drop spoonfuls of the candy melts all over the top of the white chocolate.
Use toothpicks to gently swirl the colors together.
Sprinkle on the halloween candy and colored sugar sprinkles.
Place the baking sheet in the refrigerator for about 30 minutes, or allow to set at room temperature for 2 hours.
Use a knife to cut the bark into approximately 16 pieces.