With an electric mixer, blend all ingredients on low speed for 5 minutes; for hand mixer use high speed. Color Flow icing "crusts" quickly so keep it covered with a damp cloth while using.
To "soften" or thin for filling in, add ½ teaspoon water to ¼ cup of icing (add just a few drops at a time as you near proper consistency). Color flow is ready for filling in outlines when a small amount dropped back into the mixture takes a count of 10 to disappear.
Stir in Wilton Icing Color as desired. Dried color flow will fade slightly when exposed to fluorescent and bright sunlight, so keep dried color flow pieces covered until cake is ready to assemble.
This recipe makes 2 cups plus 2 tablepoons full strength icing.