Tim,
You are making some interesting points that also confirm what I have found. Just as you say, black oxide is black, so the blue color is not really the color of the bluing. It usually appears after you oil it so it's just a trick of the light, much like what you see in a rainbow or an oil slick on water. However, I have seen guns that have a slight blue hue to them even when dry (for example, my FN/Browning 1900) but they have all been quite old. This makes me think that aging possibly does something to the finish, not to the oxide color itself but to its surface. It also seems like machined and unpolished parts often get a blue sheen to them when you rust blue, so I'm trying to figure out if there is a way to prep other parts (by wire brushing, burnishing etc) to get the same result.
I usually do the final polishing with fresh paper, as I want all parts to have the very same finish before I blue them. The grit will wear gradually so I have never had any luck getting an even prep using worn paper, it's either too worn or not worn enough. I usually use fresh 600 for the final polish, it gives the rust a good bite but is still fine enough for the rust to etch away any directional polishing marks.
And yes, I'd love to see a picture or two of your 1911. I have found that a lot of the appearance is in the accents, and I have used temper colors with good results. Nitre bluing is probably next on my agenda and the only reason why I haven't used it yet is the possible safety issues, but I'm hoping to get my shop area closed off so the family (including the £$#¤% cats) absolutely positively can't get access to it.
