In a large bowl using a hand mixer or a stand mixer fitted with a whisk attachment, beat together powdered sugar, meringue powder, and 9 tablespoons of water on high speed for 7 minutes. If the icing is thick with stifff peaks, add more water, a little at a time (or, if it’s too thin, add more powdered sugar). It’s the right consistency if when you run a knife through the icing, or when you drizzle down some icing, it blends back together/smoothes out within about 10 seconds. Add gel food coloring, a little at a time, until desired color is achieved.