You can make beautifully decorated cookies with just powdered sugar, water, and food coloring. Before you start decorating cookies, it is important to understand color theory. Primary colors are blue, red, and yellow. When you mix those colors you get secondary colors. Blue and red make violet. Red and yellow make orange, and blue and yellow make green. If you mix all three primary colors together, you get brown. To make black color, mix together green and red and a few drops of blue. Also, purple and yellow make brown. Orange and blue make brown as well. Concentration also makes your colors seem darker. The same amount of color in less water will appear much darker. If you mix water and confectioners sugar, you can make a thin syrup for a sloppy effect. If you add more confectioners sugar, it makes a paste. You can cover your cookie with this and use it as your background. Use a toothpick to place the colors where you need it, and do a design of your choice!