Make one lily 2 days in advance. Prepare royal icing following recipe directions. Tint portions yellow and three shades of green. Prepare lily nail. Use tip 366, cut disposable decorating bag and light green icing to pipe six petals, pulling out from center, in foil-lined lily nail. Use tip 14, cut disposable decorating bag and dark green icing to pipe star in center. Use damp brush to brush icing up petals. Insert trimmed brown stamens in center. Let dry overnight.