How to tint powdered sugar (icing sugar)?

I'm looking for a way to tint powdered sugar without wetting it.

I know that there are powdered food colors but I think that part of what activates the color is the fact that they get wet when you add them to an icing or batter.

I'm also afraid that they're so concentrated that, even if I get the color I want, I'll end up dyeing the mouths of the people who eat the cookies/cupcakes/whatever that I dust with the powdered sugar.

Is blending/processing colored sanding sugar and adding a bit of cornstarch an option? Will it ever mimic actual powdered sugar?