If you're working with a standard Colt (as I take from your post) and looking for something inexpensive, Novak's has a "drop in" sight that will fit the standard dovetail. Doesn't look near as pretty as a Lo-mount, but cost is MUCH less 9used to be around $30 in Brownells, or direct from Novak's).
Wilson used to offer a "Combat" drop-in sight. It fit the standard dovetail, and extended over the rear of the slide, and had a large rectangular surface. It worked very well; good sight picture, and extended sight radius by 1/2". Down side was corners were sharp, and needed to be filed round so you don't cut your forarm on them. If not still available, I may have one around if I dig for it.
Personal preference, all my guns now have Novak Lo-mounts. Not inexpensive, but in the long run worth it.