Green, black, white and yellow teas etc. all originate from the same tea plant, they differ only in the way they are processed.
To produce black tea, the tea leaves are wilted after harvesting and then rolled to release the cell sap, which in conjunction with oxygen triggers the fermentation of the leaf and gives it its characteristic colour and flavour.
The wide colour spectrum of dried black teas ranges from bright rusty red to a deep, dark brown. After fermentation, the tea is dried and sorted by leaf grade, from large-leaf teas and broken to powdery fannings and dust.
In the production process of green teas, following the wilting, various heating methods are used to prevent fermentation, e.g. steaming (Japanese method) or roasting (Chinese method). The tea thus retains its green leaf colour, which can range from a light, silvery green to a deep, dark green. Depending on the variety, the flavour varies from bitter to pleasantly sweet and aromatic.