Decorate Cake. Using a knife, trim the bottom of the cake to sit straight.
Using teal icing and angled spatula, ice train top and engine smooth
Using yellow icing with tip 5, pipe windows and top of smokestack. Smooth with spatula. Using the same bag, pipe outline around windows.
Using bright green icing with tip 8, pipe band around top of train; smooth as needed
Using bright green icing with tip 5 and pastel green icing with tip 5, pipe lines to cover smokestack. Using spatula, smooth colors together
Using pastel green icing with tip 5, pipe horizontal lines on the bottom half of the body of the train and on the back engine.
Using light orange icing with tip 5, pipe vertical lines on front of the train (cowcatcher).
Using medium blue icing with tip 12, pipe wheels. Smooth using tapered spatula, leaving the center of wheels open. Pipe center using light orange icing with tip 5.