PREPARE cake batter and bake in 13x9-inch baking pan as directed on package. Cool in pan 15 min. Invert cake onto wire rack; remove pan. Cool cake completely. Transfer cake to large platter or cake board.

TINT whipped topping with food coloring to desired shade of green; spread onto top and sides of cake.

SPRINKLE wafer crumbs in diamond shape in center of cake to resemble a baseball infield. Draw base lines with the white icing. Add a marshmallow piece for home plate and for each base. Decorate graham snacks with the colored icing to resemble baseball players; arrange on top of cake. Refrigerate up to 2 hours before serving. Store leftover cake in refrigerator.