Bluing turning Plum colored

[stock]

I have a Model 27 and a 586 which I purchased used.
The 27 has the deep black bluing everywhere except the barrel. The barrel is still very bright and shiny but has more of a plum hue to it.
The 586-1 is deep black everywhere except the cylinder which has a plum hue to it.
What causes this phenomena ? Could the barrel or cylinder have been replaced or reblued?

Any ideas or opinions would be greatly appreciated.

Thanks, John

 

[ditrina]

Here ya go..
http://smith-wessonforum.com/s-w-revolvers-1961-1980/97494-what-causes-bluing-turn-plum.html

 

[stock]

Thank you, that was a very informative thread.