Divide the powdered sugar into two gallon sized bags and set it aside.
Heat the red candy melts according to the package instructions. You want to make sure the candy is melted enough so that you can easily stir it.
Mix 2 cups of the Chex cereal with the red candy melts until all the cereal pieces are completely coated. (mix gently.. some cereal pieces will break but that’s ok)
Transfer the coated cereal to one of the bags of powdered sugar. Seal and toss to coat.
Spread the coated cereal on a baking sheet to cool.
Repeat the process with the blue candy melts.
When all the Chex have cooled, combine the red and blue cereal with the pretzels, M&Ms, and star sprinkles in a large serving bowl.