Do not adjust your monitor

The gun really is green.
This is a Springfield Armory 1911A1 in 45 ACP. Springfield released a version in olive green and to original military specs about five years ago.
The 45 has been a durable weapon for the US military, carried as the standard side arm for over 70 years. It was replaced by the 9mm Baretta, but still remains in service with some units, and for good reason.

The U.S. Military used a wide variety of side arms in the late 1800's. Most were 38 caliber Colts and Smith & Wessons. While fighting the Moro's in the Philippines, The 38 was found to be unsuitable, and the Army briefly sent 45 caliber single action revolvers to the troops. Hiriam Maxim had designed a self loading pistol in the 1880's, and this sparked interest in semi auto side arms by many nations. The US military initially tested guns from several foreign manufacturers, and evaluated a Lugar in 7.65 which was found to lack stopping power. An improved version of that was tested, the 9mm Lugar aka 9x19mm NATO.
After tests conducted in 1904, it was determined that any cartridge would need to be at least 45 caliber, and design tests continued with designs from several manufacturers. The tests eventually narrowed the field to two, Colt and Savage, and in 1911 the Colt model was selected. The deciding factor was a grueling 6000 round test in which the Colt performed flawlessly while the savage design had 37 malfunctions.
Following WW1, the pistol was modified to become the 1911A1. Changes were minor, and included a shorter trigger, cut back frame behind the trigger, and an arched main spring housing.

With those changes, the mighty 1911A1 soldiered on. Its accuracy became the thing of legends. many soldiers claimed that after firing the seven rounds in hte magazine, you then beat the enemy soldiers to death with the thing. That was not the case though. With little practice, most people can group effectively at ranges beyond fifty meters thanks to the well thought out design of John Browning.
WW2 saw the production of nearly 2 million 1911 from a variety of companies. The 1911 was even made in Norway by the Germans, and a Kongsberg Colt with Waffenamt stampings will fetch a small fortune.

Preasure from NATO for conformance was to spell the end of the 1911 though. As the pistols began to wear and break, the Army Arsenals repaired them by taking parts from other guns. By the late 1970's, the end was fast approaching, and field tests confirmed its successor, the M-9. Many units retained the 45 though. USSOCOM, and delta Force in particular were not satisfied with the 9, and in 2004 a new generation of 1911's known as the 1911A2 began testing. the 1911A2 design incorporates a variety of sights, finishes and features that are a full family of weapons adaptable to a wide variety of missions.
With that change, the 1911 will continue to soldier on well past the century mark, an impressive feat for a military arm, especially when you consider that prior to its adoption, the military was testing and adolting several new side arms a decade.
How long will the 1911 series remain in service? your guess is as good as mine. Its hard to beat perfection.