Preheat oven to 356°F or 180°C.
Beat white egg with a hand mixer at a high speed until soft peaks. Gradually add sugar, about 1 tbsp at a time. Stirring after each addition until sugar is completely dissolved.
Add lemon juice and beat again until the mixture is hard peaks and shiny.
Add sifted cornstarch to the fluff and beat until fully combined.
Divide the fluff into ⅓ and ⅔. Combine ⅔ of fluff with food colouring until mix thoroughly.
Transfer each color into a piping bag.
Prepare a baking tray with parchment paper. Add a dot of meringue mixture to the four corners between a baking tray and parchment paper.
Pipe the meringue mixture into a baking sheet and bake for 1 hour.
After 1 hour of baking, let the meringue cookies sit on the oven until completely cold.