Berets of the United States Army
U.S. Army Special Forces wear the green beret because of their link to the British Commandos of World War II. The first Ranger unit, commonly known as Darby's Rangers, was formed in Northern Ireland during the summer of 1942. On completion of training at the Commando Training Depot at Achnacarry Castle in Scotland, those Rangers had the right to wear the British Commando green beret, but it was not part of the regulation uniform at the time and was disallowed by the U.S. Army. 
The 10th Special Forces Group (Airborne) had many veterans of World War II and Korea in its ranks when it was formed in 1952. Members of the 10th SFG began to unofficially wear a variety of berets while training, some favoring the red or maroon airborne beret, the black beret, or the green commando beret. In 1953, a beret whose design was based on that of the Canadian Army pattern, and which was rifle-green in color, was chosen for wear by Special Forces units.
Uniform beret
In Portugal, the beret is worn by a number of civil security forces and emergency organizations. The colors worn are:
Black berets were worn by all members of the Singapore Police Force until 1969, when the peaked cap was introduced. The beret was, however, retained for specialist forces, such as officers of the Special Operations Command (SOC) and the Police Coast Guard, as well as the Gurkha Contingent. A dark blue beret is worn, although the Police Tactical Unit of the SOC switched to red berets in 2005. The Gurkha Contingent began wearing khaki-coloured berets from 2006. TransCom (Public Transport Security Command) officers wear light grey berets.