In a large bowl, break apart almond paste with a fork, and cream together with butter, sugar, and egg yolks. When mixture is fluffy and smooth, stir in flour to form a dough. In a small bowl, beat egg whites until soft peaks form. Fold egg whites into the dough. Divide dough into 3 equal portions. Mix one portion with red food coloring, and one with green food coloring. Spread each portion into one of the prepared baking pans.