Blueing
Perhaps if it looks a different blue on that latch, maybe it was replaced or refinished. Better inspect the gun as a whole in case it was refinished. You should compare it to the blue on another snake or a similiar Colt. Look for power buffing marks, kinda a swirly pattern and edges that look too rounded and lettering and marks that look "soft". Also buffing does not cover pits, look for small rough spots or what look like tiny pinholes. I have seen many nicely blued guns from a distance that show up these flaws upon close inspection. It is the sign of a cheap refinish job. If you call Colt, they will tell you the year your gun was made for free, instead of going out and buying a book. If you want specifics, you will have to pay for a Colt letter, not really cost effective for non expensive models.