3 carried by raiders in Brahmin Wood. One is on a raider outside the compound entrance. There's another on a raider inside the road block. Third carried by raider boss Horus inside the raider base in Brahmin Wood.
1 can be found in Freeport, inside the chest in the O'Reilly tent.
The Colt 45 appeared first in Fallout, on the cover of the Guns and Bullets magazine. Chris Taylor desired to include it as a usable firearm, but failed to do so in order to limit the types of ammunition . It was not until Fallout Tactics that it became a usable weapon.
↑Post by Chris Taylor where he stated, ‘My only regret is not including a Colt .45. It fits in the same category as the Mauser. I think it was a question of trying to keep the number of ammo types down.’