1
Line baking sheet with parchment paper and set aside.
2
Line work surface with wax paper or foil and place wire rack on top. Portion 4 tablespoons of each chocolate and place in plastic bag; snip off one corner and set aside.
3
In a microwave-safe bowl, melt all but 4 tablespoons each chocolate in 15 second bursts, stirring between each heating.
4
Working in batches of 2 to 3 Oreos, dip each in chocolate until fully coated and transfer to wire rack. (Lightly scrape the bottom of each cookie against edge of bowl to remove excess coating.)
5
Melt remaining chocolate and place each color in a plastic bag. Snip a bottom corner and pipe three circles on the opposite-colored cookie. Using a toothpick and starting from the inner-most circle, drag a line through each circle toward the edge of cookie to create web. Repeat until all cookies are dipped and decorated, then transfer to the refrigerator to set.