Preheat oven to 275 degrees F (135 degrees C). Grease cookie sheets.
In a large glass or metal mixing bowl, beat egg whites until foamy. Gradually add lemon zest and sugar, continuing to beat until whites form stiff peaks. Color light green or pink with the food coloring while mixing. Using a rubber spatula, fold in the ground almonds. Drop by heaping spoonfuls onto the prepared cookie sheet. Cookies should be about 2 inches apart.
Bake for 20 to 30 minutes in the preheated oven, until cookies are firm and slightly brown. Allow cookies to cool on the sheets for 5 minutes before removing to wire racks to cool completely.
