The style is nothing new, as ancient brewers commonly used herbs and plants for flavoring and bittering before hops were discovered.
Color can vary from quite pale to quite dark, and the spices and herbs added can vary. Some common additions are cinnamon and nutmeg during winter, ginger, juniper berries, and many others. Hops are generally quite mild (if they are present at all) in order to allow the sometimes subtle herb and spice flavors to stand out.
Best served cool, 46-54 degrees and in a stemmed tulip glass, pint glass, or beer mug.