Making multiple colors of royal icing couldn’t be easier. Figure out how many colors of icing you want and divvy up your royal icing into that number of small bowls, teacups, mugs, etc. If using gel colors, use the tip of a toothpick to add a tiny amount of the gel to the icing, stirring it until it's totally mixed in and you see the resulting color. Slowly add more gel, stirring well between additions, until the color has reached the desired shade. Remember, when coloring icing you can always add more color, but you can’t take it away. If using liquid food coloring, add the coloring one drop at a time, stirring until it's totally mixed in and you see the resulting color. Slowly add more coloring, one drop at a time, stirring well between additions, until the color has reached the desired shade. You may need to beat in a little extra confectioners’ sugar if the liquid color begins to thin down your icing. When you’ve finished, cover the surface of the icing with plastic wrap and chill each bowl as you make it until you have all the colors you need.