Shi Dai Mao (Rock Wearing a Hat) Brand Purple Pu-erh tea Varietal Cake is made up of unique purple tea. It is astringent and young, it needs time to age and mellow. The purple color comes from anthocyanin, which changes color along with cell sap acidity. High levels of acidity lead to red color, while medium acidity is more purple, and high alkalinity tends toward indigo. Use less of this tea at first to test the bitterness. A really special cake. 2009 leaf.