German Shepherds have a variety of colors, the most common of which are tan/black and red/black. Most color varieties have black masks and black body markings which can range from a classic "saddle" to an over-all "blanket." Rarer colour variations include the sable, pure-black, pure-white, liver and blue varieties. The all-black and sable varieties are acceptable according to most standards; however, the blue and liver are considered to be serious faults and the all-white is grounds for instant disqualification in some standards.
German Shepherds sport a double coat. The outer coat, which sheds all year round, is close and dense with a thick undercoat. The coat is accepted in two variants; medium and long. The long-hair gene is recessive, making the long-hair variety rarer. Treatment of the long-hair variation differs across standards; they are accepted but not competed with standard coated dogs under the German and UK Kennel Clubs while they can compete with standard coated dogs but are considered a fault in the American Kennel Club. The FCI accepted the long-haired type in 2010, listing it as the variety b - while short-haired type is listed as the variety.
German Shepherds were bred specifically for their intelligence, a trait for which they are now famous. In the book The intelligence of dogs, author Stanley Coren ranked the breed third for intelligence, behind Border Collies and Poodles. He found that they had the ability to learn simple tasks after only five repetitions and obeyed the first command given 95% of the time. Coupled with their strength, this trait makes the breed desirable as Police, guard and search and rescue dogs, as they are able to quickly learn various tasks and interpret instructions better than other large breeds.
German Shepherds are highly active dogs and described in breed standards as self-assured.The breed is marked by a willingness to learn and an eagerness to have a purpose. They are curious which makes them excellent guard dogs and suitable for search missions. They can become over-protective of their family and territory, especially if not socialized correctly. They are not inclined to become immediate friends with strangers.German Shepherds are highly intelligent and obedient
Taken from Wikipedia