By Cold, Hard Football Facts contributor Lew Bryson
Ever seen a raw coffee bean? They're actually berries, red and green.
You have to roast them to get them dark and brown, and the darker the roast – Vienna, French, Satanic – the longer you roast them. But no matter how long you roast the beans, it's still coffee, just a bit more flavorful.
Dark beers are made the same way.
Ever seen barley, the grain used to make beer? It's actually a very light tan in color. It gets a little darker when it's put through a kiln, a drying oven, as part of the process that turns it from raw barley into barley malt ... unless the maltmaker decides to make a dark malt.
And if he does, it's like coffee, literally: They shovel the malt into a drum roaster, the same kind of machinery used to roast coffee beans, and they roast it.
If you want dark beer, like brown ale or a deep, dark stout, that's how you do it: Roast your malt longer. It doesn't take that much dark malt; a little bit goes a long way. Something like a schwarzbier, a German lager whose name literally means "black beer," has a dark black color but hardly any roasted flavor at all. It's a smooth, easy-drinking black lager.
Dark beers are not necessarily "heavier" or stronger in alcohol than other beers – just like toasted bread isn't any "heavier" than plain old bread. Dark beers are simply made with more darkly roasted malts, which gives them more flavor.
You can darken a beer somewhat by adding more malt, which will give you a stronger, heavier beer. You can darken a beer a little by cooking the malt harder in the brewing process, a technique called decoction, which will give you a darker, smoother beer. 
But by far the easiest way to get a dark beer is the Juan Valdez method: Just roast it.