Preheat oven to 200 F and line two baking sheets with a piece of parchment paper.
Combine egg whites and cream of tartar in the bowl of a stand mixer fitted with the whisk attachment. If you don't have a stand mixer, you can do this in a large mixing bowl using a hand mixer, or you can use a lot of elbow grease and bicep muscles to hand beat.
Beat at medium-low speed until the eggs are frothy, about two minutes. Gradually add the sugar, continuing to beat until soft peaks form, about 5 minutes.
Add flavoring to the meringue mixture. Continue beating on medium-high speed until stiff peaks form. This means that when you remove your whip attachment and dip it in the egg white, and then flip it, the egg white will stand straight up.
Add the gel food coloring until you get the color and swirliness that like.
Transfer the meringue to a piping bag fitted with a plain round tip to make hearts. If you want to make meringue kisses, you'll want to use a star tip. To make the hearts, pipe two small upside down teardrops, with the sides touching. You'll need to increase the pressure to make the round part of the heart, and then decrease to make the pointy tip. To make kisses, place piping tip on the parchment paper and apply strong pressure for a second, then release and pull up. Pipe directly onto the prepared baking sheets.
Place sheets in preheated oven. Bake 1 hour, until the meringue is dry and can be lifted easily from the parchment, but the outside of the meringue is not browned. Turn off the oven and leave the meringue to dry out for 2 hours. Your meringue should be crunchy on the outside and with a chewy center.