a sweater-shaped cookie cutter; piping bags or squeeze bottles
Preheat the oven to 350 degrees F.
Mix the sugar cookie mix according to the package instructions and divide the dough into 3 equal dough balls. Color one dough ball red and the other dough ball green so you have 1 plain, 1 red and 1 green.
Tear teaspoon-sized pieces of each color dough and drop them on a piece of parchment or a silicone baking mat, alternating colors close together so it looks like confetti. Place a sheet of parchment or wax paper on top of the dough pieces and roll out to 1/4-inch thick. Refrigerate the rolled out dough for at least 20 minutes or up to 1 hour (this helps keep the cookies from spreading).
Using a sweater cookie cutter, press out as many sweaters as you can and place them on a parchment-lined cookie sheet. Re-roll the leftover dough and keep punching out cookies. (Note, the more you roll, the cooler the dough pattern will be, but if you over-roll it, it will become a muddy color.)
Bake just until the bottoms start to brown, 10 to 12 minutes. Remove from the oven and let cool completely before decorating.
Mix the royal icing according to the package instructions. Divide the icing into three bowls. Leave one bowl white, dye another red and the last green. Add the icing to piping bags or squeeze bottles. Outline a cookie with one color, then another inside the first outline, working in from the perimeter and alternating colors until the whole cookie is covered. Drag a toothpick from the center of the cookie out to the edges to create a tie-dye effect. Repeat with the remaining cookies. Let set until dry, 20 to 30 minutes.