Preheat oven to 350°F. Prepare cookie sheets by lining with parchment paper. (Do NOT use pan spray!)
In the bowl of a stand mixer, combine egg whites, salt, and cream of tartar. Using the whisk attachment, whip on high until glossy peaks form. Slowly add in the sugar – a little at a time – and continue whipping until stiff peaks form. Turn off mixer, remove bowl. Gently stir in peppermint extract to taste.
Working quickly but gently, divide the meringue into three bowls. Dye one red, and another green, leaving the third bowl white.
Fit one large pastry bag with a large coupler set and tip of your choice – I used used a 4B, large star tip. Fill the other three bags with one each of the three meringue colours, taking care to avoid air bubbles. I like to tie them off with a little bit of twine, as it keeps things cleaner.
Cut about 3/4″ off the end of the three filled bags and CAREFULLY insert them into the fourth pastry bag, so that the three open tips insert almost all the way into the coupler (NOT all the way into the tip, though!)
Be gentle, you don’t want to squeeze meringue out of one or both of those bags yet!
Use the frosting bag as you normally would, piping small swirls of meringue out onto the prepared cookie sheets. I like to make them just over 1″ in diameter, and leave about 1″ between each little mound.
Bake for 20-25 minutes, or until just starting to get lightly browned. Remove from oven and allow to cool fully before transferring to an airtight container.