Grease and flour 1 (9 in) round baking pan and 1 (9 in) square baking pan. Prepare the cake mix according to package directions, adding a few drops of red food coloring to batter. Remove cakes from pans and cool completely on wire racks. Trim the tops of each cake to make them an even thickness.
To form the cakes into the shape of a witch's hat, cut a 5-inch, 3 1/2-inch, 2 1/2-inch, and a 2-inch circle from the square cake layer. Press the cutter straight into the cake without twisting. Twisting can cause the cake to be uneven. Remove the scraps and use them to fill the ice cream cone. Pack the scraps firmly into the ice cream cone.
Drape a cake stand with black fabric. Place 3 pieces of waxed paper around the edges of the stand, leaving an open space in the middle. Place the large round cake in the center of the stand, on the waxed paper. The waxed paper will prevent the cake stand from getting dirty while making the cake. Ice the cake with the chocolate frosting.
Place the 5-inch circle in the center of the cake. Ice the top completely. Place the 3 1/2-inch cake in the center of the 5-inch cake. Ice the top completely. Place the 2 1/2-inch cake on top of the 3 1/2-inch cake and ice the top. Place the 2-inch cake on top of the 3 1/2-inch cake and ice the top. Insert 1 end of the skewer into the cake-stuffed ice cream cone. Press the other end of the skewer through the center of the cake layers to stabilize the cake and attach the ice cream cone.
Fit a pastry bag with a flat, thick tip. Alternately, use a resealable plastic bag and snip off 1 corner. Fill the bag with the remaining frosting. Pipe icing onto the cake from the 5-inch layer, up to the tip of the cone. Using this method, pipe icing all around the cake. Don't worry if everything is covered. Once the icing is roughly piped on, holding the tip of the ice cream cone, spread it evenly on the cake with a spatula.
To make the hat band: Cut a 2-inch piece of marzipan off the tube. Dust a work surface with confectioner's sugar. Place a few drops of food coloring on the marzipan and knead with your hand until desired color is reached. Roll out the marzipan, dusting the surface with confectioners' sugar as necessary to prevent sticking. Roll out to a 17-inch long rectangle that is about 1/8-inch thick. Cut into a 16-inch long by 1-inch wide strip. Brush the strip lightly with corn syrup. Sprinkle with colored sugar crystals. Set aside to dry for 15 minutes. Use extra marzipan for another purpose.
Wrap the hatband around the 5-inch cake. Decorate the cake with candy. Hold the cake still with a spatula and gently pull out the waxed paper.