In a food processor, pulse together the almond flour and the powdered sugar.
Add in 2 egg whites to the almond mixture and process until smooth (the texture will be like almond paste).
Add in food coloring of your choice and continue processing until the color is all blended in
Put the mixture in a large bowl and set aside.
In a saucepan bring the water and sugar to a boil and cook for about 15 minutes, or until a candy thermometer reads 110 degrees-celsius.
In the bowl of your electric mixer beat 2 egg whites until soft peaks form.
Slowly add in the hot syrup and continue beating until firm peaks form and the meringue has cooled.
With a spatula, gently fold in 1/4 of the meringue into the almond mixture.
Continue folding the meringue until completely incorporated.
Prepare two baking sheets with parchment paper.
Fit a piping bag with a 3/8-inch round tip and fill it with the macaron mixture.
Pipe the batter onto the baking sheets.
Let dry at room temperature for 1 hour.
Preheat oven at 275 F.
Bake the macarons for 20 minutes; rotate the baking sheet after 10 minutes for even baking.
In the meantime prepare the buttercream.
Set buttercream aside and remove macarons from oven and transfer to a cooling rack; do not remove from the parchment paper, yet.
After they have completely cooled, turn half of the caps on their backs and pipe about 1/2 teaspoon of the filling onto it and cover with another cap.
Once all of your macarons are assembled, put them in an airtight container, in the refrigerator and let them rest for another 24 hours.