The blueing differences you see in Figure 1 are the result of bluing salt tank chemistry differences as the tank fluid is used over an extended time- in an industrial setting, not all parts are necessarily blued together, and so some may be used that had this 'plum' coloring. You see 'two-tone' issues with P38s, with the frame and slide showing differences, for example. Sometimes it is also a matter of steel alloying and consistency, although in this case I believe the former to be the cause. Not the Russians.