Line a baking sheet with parchment paper to prevent sticking and for easy cleanup.

Melt the white chocolate wafers according to the package instructions. Dip each Oreo halfway into the melted chocolate, then place it on the parchment-lined baking sheet. Let the chocolate set completely. For faster results, place the cookies in the fridge for a few minutes.

Melt the green chocolate wafers following the package directions. Transfer the melted green chocolate into a piping bag with a fine tip for precise decorating.

Pipe small Christmas tree shapes onto the white chocolate-dipped section of each Oreo. Start with a narrow base and work your way up to form the tree shape.

While the green chocolate is still soft, sprinkle with multicolor sprinkles to mimic ornaments or lights. Let the cookies cool completely before serving or storing.