Earl Grey tea is any tea blend with a distinctive flavour and aroma derived from the addition of oil extracted from the rind of the bergamot orange, a fragrant citrus fruit. Traditionally the term "earl grey" was applied only to black tea; however, today the term is also applied to both green and white teas that contain oil of bergamot.

The blend is named after the 2nd Earl Grey, British Prime Minister in the 1830s, who reputedly received a gift, probably a diplomatic perquisite, of tea flavoured with bergamot oil. The legend usually involves a grateful Chinese mandarin whose son was rescued from drowning by one of Lord Grey's men, although this blend of tea was first made from fermented black Indian and "Ceylonese" (Sri Lankan) teas.

Green tae is much more popular in China than black. Thus, it seems somewhat unlikely that they would have had a recipe for what we now call Earl Grey to bestow on visitors, though over the years many other varieties of tea have been used. Also, Lord Grey never set foot in China. In another version though, it's the son of an Indian raja being rescued from a tiger by one of Grey's servants.

The tea proved so popular in the Prime Minister's drawing room that his tea merchants, Twinings in the Strand,were given a sample and asked to come up with a close match. Twinings sold the first "Earl Grey's tea" in the British market.

Twinings Earl Grey blend includes China tea, Indian Darjeeling, Ceylon, and a hint of Lapsang souchong, a strong, "smoky" black tea. Although it is often served black (without milk), many of the upper classes (contrary to belief) drink it with a little milk (which gives the tea a murky grey colour, similar to that of dull washing up water).

Source: http://en.wikipedia.org