Great idea. I went looking for food glitter. Too expensive, but I did see a lot of sites on "How to make your own glitter sugar." They all say to mix the coloring and the sugar with a fork. When I make the Christmas Wreath Cake, I put green coconut all around the outside. I put the coconut in a large container that has a lid. (An empty canister works great. Lots of room to shake the contents.) Add the coloring and shake like mad. It colors all the coconut. I suspect that the same would apply to sugar.
Illegitimi non carborundum!
I don't want my last words to be, "I wish I had spent more time doing housework"