Tint a portion of dough green using icing color. Roll out plain and green dough.
Cut stars from plain dough using mini star cutter from set. For each tree, cut 2 tree cookies using Comfort Grip cutter; cut one of the trees in half. bake and cool all cookies.
Position whole tree cookie on waxed paper-covered board. Using melted green candy in cut parchment bag, pipe a line down center of cookie. Attach one tree half; refrigerate until firm. Repeat, attaching 2nd tree half to other side of cookie; refrigerate until firm. Ice star cookie smooth with yellow icing. Sprinkle with yellow sugar. Let dry.
On tree cookie, pipe tip 3 zigzag garlands in white. Position nonpareils on garlands. Attach star cookie to treetop with melted candy; refrigerate until firm.