Line a baking sheet with parchment paper. Fit a piping bag (or several, if making different colors) with a small round tip.
In a small bowl, whisk the confectioners' sugar, egg white and salt. The consistency should be slightly thicker than glue. Stir in a bit of water if it is too thick or more confectioners’ sugar if it is too thin.
Tint the mixture with food coloring (or divide among bowls and tint each a different color). Transfer to the piping bag and pipe lines onto the prepared baking sheet. Let dry at room temperature until completely set, at least 4 hours or overnight.
Scrape the lines off the paper and break into sprinkles.