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.
Military beret
Icelandic armed services commonly use berets.
The beret is the standard headgear for the Indian Army. Berets are worn by officers and other ranks, apart from Sikhs, who wear turbans. The beret colours worn by the Indian Army are as follows:The beret is the standard headgear of armed forces and police personnel in Indonesia. It is also worn by paramilitary and other uniformed services in the country such as the Fire Brigade, Search and Rescue, Scouts, civil militias (such as "Banser") and civil paramilitary organizations. In the Military Services (Army, Navy and Air Force), the berets are dragged to the right (the insignia are worn on the left side), while in the Indonesian National Police force and Military Police Corps, the berets are dragged to the left (the insignia are worn on the right side). Both having its own meaning, dragged to the right meaning "ready for combat and defense" and dragged to the left meaning "ready for law enforcement and order". 
Military and Police services according to their beret colours which represent different units within the force are as shown below:The beret color system used for the different branches of the Iraqi military and security forces changed after the fall of Saddam Hussein.
Beret colors currently (and formerly) worn by Iraqi forces are as follows: