Prepare the marzipan
Knead the marzipan with your hands to soften it up and add the green and yellow food coloring sparingly until you have achieved a bright, spring green. Flatten the marzipan into a disk. Place it between two pieces of parchment paper or on a smooth surface dusted with powdered sugar and roll it into a thin, even circle ideally about 1/32″ (just under 2mm) thick but do the best you can to thin it out. Keep in mind the circle has to be large enough to cover the entire cake. You can dust the marzipan and work surface with powdered sugar if need be to prevent sticking.