Amber Ale (also often known as Red Ales or American Ales) are a more modern, non-traditional style, and many of these beers borrow heavily from the characteristics associated with more classical styles such as "Pale Ales" or "Bitters." Amber ales are light to medium bodied and can be anywhere from light copper to light brown in hue. They can vary from generic and quaffable to serious craft brewed styles with extravagant hoppy aromas and full malt character. Typically amber ales are quite malty but not heavily caramelized in flavor.
A small amount of crystal or other coloured malt is added to the basic pale ale base to produce a slightly darker colour, as in some Irish and British pale ales. In France the term "ambrée" is used to signify a beer, either cold or warm fermented, which is amber in colour; the beer, as in Pelforth Ambrée and Fischer Amber, may be a Vienna lager, or it may be a Bière de Garde as in Jenlain Ambrée. In North America, American-variety hops are used in varying degrees of bitterness, although very few examples are particularly hoppy. In Australia the most popular Amber Ale is from Malt Shovel Brewery, branded James Squire in honour of Australia's first brewer, who first brewed beer in Sydney in 1794.
History: Known simply as Red Ales in some regions of the States, these beers were popularized in the hop-loving Northern California and the Pacific Northwest areas before spreading. American Amber is derived from American Pale ale and shares many of the same characteristics including a fairly high hop rate with American hops for flavor and aroma. Ambers have higher mouthfeel and body than corresponding American Pale Ales. Many are reddish in color and are also closely related to Irish red ales, except that they use more floral accented hops. American Ambers were pioneered by Craft Beer brewers on the American West Coast, but quickly spread to other parts of the country and eventually stood as a style on its own.
Aroma: Low to moderate hop aroma from dry hopping or late kettle additions of American hop varieties. A citrusy hop character is common, but not required. Moderately low to moderately high maltiness balances and sometimes masks the hop presentation, and usually shows a moderate caramel character. Esters vary from moderate to none. No diacetyl.
Appearance: Amber to coppery brown in color. Moderately large off-white head with good retention. Generally quite clear, although dry-hopped versions may be slightly hazy.
Flavor: Moderate to high hop flavor from American hop varieties, which often but not always has a citrusy quality. Malt flavors are moderate to strong, and usually show an initial malty sweetness followed by a moderate caramel flavor (and sometimes other character malts in lesser amounts). Malt and hop bitterness are usually balanced and mutually supportive. Fruity esters can be moderate to none. Caramel sweetness and hop flavor/bitterness can linger somewhat into the medium to full finish. No diacetyl.
Mouthfeel: Medium to medium-full body. Carbonation moderate to high. Overall smooth finish without astringency often associated with high hopping rates. Stronger versions may have a slight alcohol warmth.
Overall Impression: Like an American pale ale with more body, more caramel richness, and a balance more towards malt than hops (although hop rates can be significant).
Comments: Can overlap in colour with American pale ales. However, American amber ales differ from American pale ales not only by being usually darker in color, but also by having more caramel flavor, more body, and usually being balanced more evenly between malt and bitterness. Should not have a strong chocolate or roast character that might suggest an American brown ale (although small amounts are OK).
Ingredients: Pale ale malt, typically American two-row. Medium to dark crystal malts. May also contain specialty grains which add additional character and uniqueness. American hops, often with citrusy flavors, are common but others may also be used. Water can vary in sulfate and carbonate content.
Source: wikipedia: https://en.wikipedia.org/wiki/Pale_ale#Amber_ale, BJCP: http://www.bjcp.org/2008styles/style10.php#1b, BrewWiki: http://brewwiki.com/index.php/Amber_Ale, Tastings.com: http://tastings.com/beer/british_ales.html