In advance: Make 40 lights in various colors using royal icing. On waxed paper, pipe tip 8 bead; add tip 2 outline hanger at top. Make extras to allow for breakage and let dry. Mold 7 candy gifts using painting method. Refrigerate until firm; unmold.
Place cake on foil-wrapped board, cut to fit. Pipe tip 3 trunk and leaf lines in buttercream; cover trunk and leaves with tip 16 stars. Position lights and candy gifts.
**Combine Christmas Red with Red-Red for red shown. Combine Golden Yellow with a little Lemon Yellow for yellow shown. Combine Leaf Green and Kelly Green for dark and light green shown. Combine Orange, Golden Yellow, Brown and Red-Red for dark brown shown on trunk lines. Combine Orange, Golden Yellow and Brown for light brown shown on trunk.