Good Question, Being a WWII history buff, I researched and found this on a website.

The best remembered "trademark" of General Patton is the ivory handled Colt .45 Peacemaker that he wore.

During the early days of WWII, when the news media was discovering that Patton was good copy, Patton was often referred to as "two-gun" Patton, alluding to the suggestion that Patton wore two ivory handled Colt .45's all the time. These reports are not wholly correct on two counts.

First, Patton neither owned nor wore two "matching" Colt .45's. The pistol commonly thought to be a Colt was actually a Smith & Wesson .357 Magnum. It was never worn as often as the Colt.

Secondly, the "two-gun" image of Patton is largely a creation of some inventive reporter. According to extensive research, there exists only one photograph of Patton wearing two ivory-handled revolvers at one time. Of course, Patton never said anything to hamper the image created by the media, since it served his purpose. The photograph spoken of was taken of Patton standing on the beach on the day of his landing at Fedala, North Africa with his Western Task Force in November of 1942. It was the first major American naval invasion in the history of the United States.

The rest of the story is at the following link. Pretty interesting reading

The Unknown Patton Chapter Five (The General's Personal Sidearms)