Preheat the oven to gas ½, 130°C, fan 110°C. Line 2 baking trays with either parchment on or a silicone mat.
In a bowl, add the egg whites and sugar then hand whisk the two together until the are incorporated.
Using a stand mixer (if you have one) whisk until the mixture is white and stiff*.
You will need a piping bag with a star or round nozzle for each colour. Using a small paintbrush, apply three stripes of colouring gel to the inside of the piping bag, from the nozzle to the opening.
Fill with meringue mixture and pipe kisses on the trays.
Bake for 40 mins, swapping the shelves half-way to ensure both trays cook evenly. Leave to cool completely before packaging up.
Notes
*You should be able to tip the bowl upside down and the mixture should not move.