Note on icing sugar: this is one of my older recipes, when icing sugar was still a part of my baking... If you're looking for a refined sugar-free option, you can make your own from raw cane sugar {process in a food processor or coffee grinder in small batches with a tiny hint of tapioca starch} {this might make it just a tinge healthier ;-) }.
Note on food coloring: my two favorite go-to brands are: India Tree & Seelect.