Doppio and Assam Black Tea are produced all around the globe. And they change according to region in where they are cultivated. So, the question arises what is Doppio and Assam Black Tea's differentiating factor?In following section we will take a close look at what is Doppio and Assam Black Tea color, serving style, types and much more. First thing to know is what are the different types of Doppio and Assam Black Tea. Well, Doppio types include Espresso while types of Assam Black Tea are Hunwal Assam Tea, Tarajulie Assam Tea, Assam Decaf, Assam Organic.