Heat oven to 325º F
In large mixing bowl, break up almond paste with a fork, add butter, sugar. egg yolks, almond extract and salt. Mix well by hand or with an electric mixer on slow speed
In separate bowl beat egg whites until stiff. Fold egg whites into almond mixture Blend in flour 1/4 cup at a time, until just incorporated.
Using a kitchen scale divide the dough into 3 equal portions. With the food coloring, color one red and one green, leaving the third white. Add enough food coloring for your desired shade.
Spray, (3) 13 x 9 inch pans with non-stick spray. With a wet spatula spread one portion of dough into each pan. Make the layers as even as possible. Bake for 10 - 15 minutes or until edges become slightly brown, DO NOT OVER BAKE. Cool. Remove from pans by covering with a cookie sheet and inverting them onto the cookie sheet.
Placing the green layer on the bottom, spread 1/2 cup of the preserves. Cover with the uncolored layer, spread the remaining preserves. Top with the red layer.
Cover with plastic wrap and cookie sheet. Place stacked layers in the refrigerator. Place jars or cans on top of cookie sheet, to weigh down the layers. Refrigerate over night.
Remove from refrigerator, unwrap the cookies. On a cutting board. Slice off hard edges. Cut into 1" strips. Carefully place cookies on a wire rack. You will need to protect your counter by placing wax paper under the wire rack.
In a small saucepan melt the chocolate and shortening over medium-low heat Pour the chocolate over each strip making sure each side is covered. Allow to set. Cut the strips into squares.