Prepare the cake mix according to package directions. Pour batter into a greased and floured 13x9x2-inch baking pan. Bake according to package directions. Cool 10 minutes on wire rack; remove from pan. Cool completely.
In a large mixing bowl, beat shortening, vanilla and almond extract with an electric mixer on medium speed for 30 seconds. Gradually add 3 cups of the powdered sugar, beating well. Beat in 3 tablespoons of the water. Gradually beat in remaining powdered sugar and enough water to make a spreading consistency. Remove 3/4 cup frosting and set aside. Remove 3/4 cup frosting; add enough blue food coloring to make desired color. Remove 1/2 cup frosting; add enough yellow food coloring to make desired color. Set colored frostings aside.
Cut the cake as shown. Assemble cake pieces on a large serving tray, using white frosting to attach pieces.
Frost the top and sides of cake with white frosting. Fill a pastry bag fitted with a star tip (#28 or #35) with reserved 3/4 cup white frosting. Decorate cake as desired. Using a pastry bag fitted with a writing tip (#2, #3, or #4) and some of the blue frosting, draw the outline of a Hebrew letter on top of cake. With a pastry bag fitted with the star tip and remaining blue frosting, fill center of the letter. Using a pastry bag fitted with the writing, star, or rose tip (#104) and reserved yellow frosting or any remaining blue frosting, add additional decorations to cake. Makes 12 to 16 servings.