Place oreo cookies into a resealable plastic bag, seal, and gently hit with a rolling pin to break cookies into pieces. Set aside.
Line an 11x15" jelly roll pan (or regular 9x13" pan), with aluminum foil and spray very lightly with cooking spray. Set aside.
Place a small saucepan with about 1 inch of water on the stove and heat on LOW until barely simmering. Pour bright white candy melts in a large glass bowl (that fits inside the saucepan so that the bottom of the bowl does NOT touch the water).
Place bowl over the top of the saucepan, creating a double boiler. Use a rubber spatula to stir candy melts until melted and smooth. Do not allow any liquid to come in contact with the candy melts.
Pour red candy melts in a small microwaveable bowl, and pour blue candy melts in another microwaveable bowl.
Microwave the blue candy melts at 70% power, in 30-45 second intervals, until most of the way melted. Remove from microwave and stir to let the residual heat melt the remaining bits.
Repeat process with the red candy melts.
Pour melted white candy melts into jelly roll pan and use rubber spatula to smooth into an even layer.
Alternate drizzling melted red candy melts and blue candy melts in vertical lines over the surface of the melted white candy melts. (you could also just spoon bits of red and blue in a non-pattern over the surface as well).
Using a small wooden skewer or butter knife, swirl in a figure eight pattern to swirl the red and blue into the white. Repeat over the entire pan. You're not looking for a pattern here, just pretty swirls.
Sprinkle swirled candy melts with oreo pieces, m&m's, star sprinkles and jimmies.
Refrigerate for 1-2 hours, or until hardened.
Lift edges of aluminum foil to remove bark from pan, and separate the bark from the foil.
Break into pieces.
Keep refrigerated until ready to serve.