Dang, Eric...but I guess inquiring minds want to know. I'll get you started, but only basic headlines. For the rest, try searching the site for each topic/question because all of this has been discussed before, albeit scattered all over the posting board. For tech stuff like this, Wikipedia is a good start.
http://en.wikipedia.org/wiki/Bluing_%28steel%29
Bluing is basically a thin coating of oxidized iron. It's applied in a controlled way to yield a finish that is tight and close. Since the resulting oxide sits on the surface of the steel, it protects the raw metal beneath by sealing it off from the oxygen in the air.
The colors/tones of the finish are influenced by the chemistry used to establish it. Though the processes are general, it wouldn't surprise me that different manufacturers' formulae would be slightly different in content and proportions of chemicals, thus slightly different in absolute color.
Lugers were all rust blued until '37, when Mauser, the main, remaining factory that produced them, changed to hot/salt/dip bluing process to save time and thus money.
I'd say the dip bluing is slightly more durable than rust blued finish, because it is physically thicker and therefore better able to seal the surface of the steel. Most attractive? That's in the eye of the beholder!
"Strawing" results when a piece of steel is heated to the exact temperature needed to turn the top molecules a gold-ish yellow. This color is one in the spectrum or rainbow effect the surface of metal turns when heated gradually on one end. Straw is from one of the lower temps, so that would be farthest from the heated end. Other colors include brown, "fire blue", purple, and finally black, the last being the result of heating the piece to red hot before cooling, and puts the "black" in blacksmith. Strawed small parts is not exclusive to Lugers. But I believe it would be more commonly found on early firearms and high end firearms.