While the aquafaba is chilling, grind the almonds, powdered sugar and food coloring in a food processor. Then sift into a bowl with a sieve. It will take several grinding and sifting processes. I ended up with 25g left of the almond-sugar mixture that I couldn't grind any finer,* which I used elsewhere for other dishes.
Cover the baking tray with baking paper. To make the macarons evenly sized, paint round circles on the baking paper. For example, shot or shot glasses are suitable for this. Do not forget to turn the baking paper afterwards, otherwise the color of the pen will rub off on the macarons.
Once the aquafaba is really cold, put it in the bowl of the food processor together with the cream of tartar and beat for about 3 minutes until frothy.
Then, step by step, add the sugar and continue beating on high speed. The mixture becomes white and glossy. Continue beating for about 5 minutes. The mixture is ready when it no longer drips from the beater of the food processor, is stiff and you can form a figure eight with it in the air.
Add almond powdered sugar mixture and mix in briskly with a dough scraper. Then pull the dough mixture over the bottom of the bowl with a spatula.
Fill the macaron mixture into a piping bag with a normal round nozzle. Use the piping bag to pipe dots onto the pre-drawn circles on the baking paper. Continue until all the mixture has been used up.
To give the macarons a nice surface and the typical little feet, hit the baking tray several times with a lot of force on a flat surface (e.g. table) or let it fall. This allows the air in the dough to escape.
Let the macarons dry for 2 hours. They are ready as soon as you can run your finger gently over their surface and nothing sticks to your finger.
30 minutes before the macarons are ready to bake, preheat the oven to 110° Celsius.
Bake the macarons in the middle of the oven for 30 minutes. Then turn off the oven and let stand for another 25-30 minutes with the oven closed. Then remove the macarons from the oven and let them cool completely.