Oolong Tea is half way between green and black tea. The tea leaves are allowed to ferment a little bit, but not as much as for making black tea from them. As well, larger, older tea leaves are used.
The leaves are picked, and allowed to wither in the sun. Then, they are rolled, to break them. This releases enzymes, and allows the oils in the leaves to start interacting with air, beginning the oxidation process, during which they start to turn dark.
Some processors, instead of rolling them, just shake them vigorously in a basket to bruise the edges, lay them out to dry in the shade, then repeat the process several times. This causes the edges of the leaves to oxidize and turn dark, while keeping the rest of the leaf green.
A human judges when the leaves have oxidized enough, at which point the leaves are toasted in a pan to stop the oxidization process. Then, the leaves are rolled again.
The tea leaves will come out anywhere from dark green to a black colour, depending on the technique and timing used.
Oolong Tea is made in China and in Taiwan.
Dark-Coloured Oolong Teas: Brew with boiling water. Use 2 teaspoons of tea leaves per 250 ml / 8 oz of boiling water, and steep for 7 minutes.
Light-Coloured Oolong Teas: Brew with water that is 180 F (when small bubbles are just starting to form at the bottom of the water.) Use 1 teaspoon of tea leaves per 250 ml / 8 oz of boiling water, and steep 3 to 5 minutes.