The yellow leaf teas of Fujian and Anhui provinces in China are highly prized. Rare, expensive and available only in small quantities, these teas were imperial treasures from the Song Dynasty through the Great Qing Dynasty (1644-1912 A.D.), and sometimes were referred to as the Emperor's Tea since historically the color yellow was reserved for the imperial court (viz. emperor's robes, etc.). Even today the color a little cachet in gifting and in the promotion and marketing of this group of teas.
One noteworthy feature of yellow teas is is the non-enzymatic oxidation that occurs when the leaves are covered. The leaves are not shaken (as is the case with Oolong processing) but as they rest in the enveloping warmth, some slight bit of oxidation occurs.