This is a light sabre cake made for a friend's 19th birthday celebration.
You get a box of cake mix and bake it according to the instructions. Buy some frosting and food coloring, and mix the colors. Use a knife to spread the frosting all over the cake. For fine decorations, put the frosting in the corner of a zip lock bag, cut the corner of the bag, and squeeze the frosting out to decorate. Voila!