4v50 Gary has it right.
The Colt hammer and trigger cannot be "re-fitted". If the trigger's sear surface or the hammer's cocking shelf has been altered, the only "fix" is parts replacement.
Nor is this a question of a too-light trigger return spring, since the Colt doesn't HAVE a separate trigger spring.
Occasionally, the S&W develops "push off" after an action job, and this can usually be corrected by a TINY amount of work on the trigger surface.
In ALL cases, if the hammer of a DA revolver has been altered AT ALL, the part needs to be replaced.
So, the bottom line is, your Colt needs the services of a pro pistolsmith who's qualified to work on the older Colt revolvers.
Unfortunately, these people are very rare today.
I can recommend Cylinder and Slide, and Pittsburgh Handgun Headquarters.