Whip the egg whites until they're foamy. Add the granulated sugar slowly and mix until the mixture is glossy and silky. Sift almond flour and icing sugar together and carefully fold it into the meringue while adding the food coloring. Add as much coloring as you need to achieve your favorite color; the amount depends on the quality of your food coloring gel.
Line a baking tray with baking paper, fill the mixture into a piping bag (you can simply cut the tip off the piping bag or use a round nozzle) and pipe round shapes (diameter 3-4 cm) onto the baking tray.
Let sit for an hour.
Bake at 175°C (top and bottom heat) for 8-12 minutes and let your macarons cool down until you fill them. The macarons in the pictures are filled with lemon curd.