Throughout the story, the color in the film begins to drain to monochrome, thus representing the central character's deteriorating health as the poison steadily takes its toll (until it is in black-and-white, as in the opening - presumably showing the flashback catching up to the current time-line of the story).
Towards the end of the film, Dexter fires a pistol, a Colt M1911A1 (standard US military pistol in the period). When the pistol is shown in Dexter's hand after he's fired it, the hammer is down. If the scene had been continuous then the hammer would still be cocked as the recoil from the shot cocks the hammer, ejects the empty shell and loads the round for the next shot.