Oolong tea is a traditional Chinese tea.
It’s made from the leaves of the Camellia sinensis plant, the same plant used to make green tea and black tea. The difference is in how the tea is processed.
All tea leaves contain certain enzymes, which produce a chemical reaction called oxidation. Oxidation is what turns the green tea leaves into a deep black color.
Green tea is not allowed to oxidize much, but black tea is allowed to oxidize until it turns black. Oolong tea is somewhere in between the two, so it is partially oxidized.
This partial oxidation is responsible for oolong tea’s color and characteristic taste. However, the color of the leaves can vary between different brands.