IPAs are the youngest style of the bunch, but probably the most popular in the US today. India Pale Ales are of a color similar (or slightly darker) to that of pale ales, but they have much more concentrated hop aroma and flavor.
Stout variations include dry stouts (such as Guinness), sweet or milk stouts (made with lactose), oatmeal stouts (made with oatmeal), or American stouts (which taste hoppier than the rest). What unites them all is that they are made with deeply roasted malt, resulting in a dark brown to jet black color, with espresso, unsweetened chocolate, or burnt bread flavors.
The beer is pale gold and fairly clear, with a spicier, more floral hop bouquet than an American lager. It's crisp and refreshing with a complex maltiness, and get its bitterness from noble Czech hops called Saaz hops.
German Hefeweizens, such as Weihenstephaner or Paulaner Hefeweizen, are known for strong banana and clove flavors from chemicals known as esters and phenols, respectively. They generally have a lower alcohol content than many other styles, and can range widely in flavor intensity.