LINE up cakes on large serving platter for train cars.
CUT a 2-in. crosswise slice off front cake; place at the back end of the first cake to resemble the train engine. Repeat with the last cake, placing the removed cake slice on the middle of the cake to resemble the caboose.
DIVIDE the whipped topping among 4 small bowls; tint with food colouring as desired. Use to frost cakes. Decorate as shown in photo.