In the bowl of an electric mixer fitted with a paddle attachment (or using a handheld electric whisk), combine confectioner's sugar, egg white, extract and salt. Mix the ingredients on low speed until a paste forms. The paste should have the consistency of liquid glue. Scrape down the sides of the bowl and continue mixing until all the confectioner's sugar is fully incorporated.
Divide the paste into as many portions as you have colors (although, this recipe works best with a maximum of 3 colors), tinting each batch with the color of the choice. Use a rubber spatula to stir the food coloring into the paste until it is an even color.
Transfer the different colored pastes into their own pastry bags, each fitted with a small pastry tip (I recommend Wilton's #2 or #3). Pipe out long, thin lines on a cookie or jelly roll pan, ensuring that the lines do not touch each other. Repeat the process with the remaining colors and allow the piped lines to set, uncovered in a dry place, for 24 hours.
Once the piped lines have dried completely, inside and out, use a bench scraper or a butter knife to break and/or chop the piped lines into short, sprinkle sized pieces. Use immediately, or store in a dry, airtight container for up to 1 month.