In a bowl, combine flour and sugar. Mix in egg whites and food coloring with hand scraper until combined. In a stand mixer fitted with a whip attachment, combine thawed egg whites and egg white powder. Mix on low speed. While whites and powder are mixing, heat sugar and water to 112°C in small heavy saucepan. Increase mixer speed to medium. When syrup reaches 115°C, increase mixer speed to medium-high. Egg whites should be at full volume, pulling from sides, and rippling toward the center. When syrup registers 116°C, slowly drizzle it into whipping whites while on medium speed. Increase mixer speed to high after syrup is added and mix until meringue cools to 50°C. Fold one-third meringue into almond flour-whites mixture. Gently fold in remaining meringue.
When no streaks of meringue are visible, deflate mixture with a rubber spatula until batter falls slowly from spatula in ribbons (like honey). Transfer batter to pastry bag fitted with plain #3 tip. Hold bag perpendicular to a silicone baking-mat lined sheet tray, about ½ inch above it. Steadily pipe 1½-inch diameter rounds onto tray. Tap tray slightly to release air from batter. Let macaron rounds dry at room temperature until skins form and top of macarons are firm to touch. Preheat oven to 345°F. Transfer to oven and lower heat to 325°F. Bake 10½ minutes. Remove from oven and cool completely. Peel macarons from tray. Fill and serve as desired and refrigerate overnight.