Preheat oven to 200F. Line a baking sheet with parchment paper (I used my imitation Silpat).
Using an electric mixer, beat egg whites and salt on medium high speed until white and foamy, about 1 minute.
With mixer running, gradually add sugar in 3 additions, beating for about 2 minutes between each addition. Beat until firm peaks form, about 2 minutes longer.
Add powdered sugar and peppermint extract; beat to blend, about 1 minutes.
Dot coloring over surface of meringue; do not stir (the coloring will form swirls when piped). Spoon meringue into a pastry bag fitted with a 1/2" tip. Twist top and pipe 1" rounds onto prepared sheet or Silpat. Space meringues 1" apart.
Bake meringues until dry, about 2.5 hours. Let cool completely (for about an hour). Meringues will crisp as they cool.
Meringues can be made 2 days ahead and stored at room temperature in an airtight container. The recipe above yields about 75 meringues.Source: Bon Appetit magazine, December 2011 issue, page 88