I tried printing parts of a Colt 45, but strangely they did not fit together. I have not determined why any given site would include incompatible parts. The barrel that I printed did not fit within the slide.
Rather than trying to figure this out, I found a 3D model of an assembled Colt 45 and printed that instead. I made sure to NOT make it black so that I do not confuse or alarm anyone.
Here are some gallery shots of the 3D print.