Cover cookies by dipping them in the cinnamon icing. Use a knife to scrape off the excess and clean up the edges. Set aside to harden.
Separate royal icing into three bowls. 1/4 in two of them and 1/2 in the third. In one of the small bowls, make black icing. In the other small, make the maroon. I used mostly red with a couple drops of yellow and green. In the largest, make your brown icing. I used about 57 drops of red, 45 green, and 11 yellow.
Stir and check the consistency of your icing. You want 15-second icing, which means, if you run a knife through it, it takes about 15 seconds to fill back in. If it is too thick, add a little water to it in 1/4-teaspoon increments. If it becomes too thin, stir in a little sifted powdered sugar.
If your cookies are firm enough to handle without smudging the base icing, you can begin piping. Otherwise, cover the royal icing and wait.