Im not sure what you did or how long it might last, but I've done the same thing you did once. I have a Fox SW which before I had it case colored had not too bad colors overall. The colors on the trigger plate were really worn and I too put a little cold blue on and did seem to bring back some of the color and/or contrast. I tried a few cold blues including Belgium Blue and Oxpho blue but ultimately had it completely re colored.
Maybe someone here could chime in, but I think your cold bluing just re colored the metal and brought out some of the original pattern that may have been barely visible. Id guess that it will last as long as cold blue would normally last.
Take care
