Prepare 2 baking sheets with silicone mats, teflon, or templates and parchment paper. Fit a piping bag with a round piping tip. Set aside. Preheat oven to 290°F.
Pulse the powdered sugar, almond flour, and hazelnut flour in a food processor and sift into a bowl. Discard any large chunks. Whisk the dry ingredients and set aside.
Combine the egg whites and powdered color. Mix with a fork just to combine.
In a clean stand mixer bowl, combine the sugar and the egg whites. Whisk to combine and place bowl over a double boiler. Heat, whisking regularly, until the sugar dissolves, about 90 seconds. Remove the bowl from the double boiler and carefully dry off the bottom.
Place the bowl in the stand mixer and whisk on a medium speed (KitchenAid 4) until you have stiff peaks, about 10- 15 minutes. (I like to do 5 minutes on speed 6, check my peaks, then speed 4, but I stop to check the peaks every minute. This method takes me about 6- 10 minutes total.)
Add the dry ingredients to the bowl and begin folding the ingredients together. Once everything is combined, continue folding until the batter flows slowly like lava.
Pipe macaron shells onto prepared baking sheets. If desired, sprinkle finely crushed hazelnuts onto some of the macarons. Let the macarons dry until you can lightly brush the tops with your finger (30 mins for me). Bake for 21 - 23 minutes, rotating halfway through. Gently poke shell, if it is firm, remove from the oven to cool. If they wiggle, add another minute or two.
Let the macaron shells cool on the sheet for 10 minutes before transferring them to a cooling rack.