Dip cookies. Melt light cocoa and white Candy Melts candy, separately, according to package directions. Use dipping scoop to dip cookies in melted candy. Place dipped cookies on rack over parchment-lined pan. Tap to smooth and remove excess candy. Chill until firm, about 5 to 10 minutes. Reserve remaining candy.
Drizzle cookies. Use drizzling tip from set, decorating bag, and reserved melted candy to drizzle lines in contrasting color on cookie. Chill until firm, about 3 to 5 minutes.