The barrel and cylinder of a 642 are stainless, and the frame aluminum alloy. S & W has made polished alloy framed guns in the past, like the models 38 and 42, but as a rule they do not refinish alloy guns. Finding an earlier, more nicely finished gun may be your best option.
Thank you for the answer. I guess the finish will have to stay the same. I will not let vanity cause me to get rid of one of the best snubbies I have ever owned.
S&W has always claimed they would not "change" the finish on the Aluminum guns, such as from blue to Nickel, but they would refinish in the same finish as original. Call customer service, 800-331-0852 and ask. If you have the plain anodize and want black they may do that.
If your original finish is bad enough, you may also want to consider KG Gun Kote, Cerakote or some of the other aftermarket high tech coatings available for firearms. If the finish on my daily carry 638 ever gets to the point that it bothers me, I plan to order up some KG Gun Kote and do it myself. When and if that ever happens I'll probably change the color to matte black, or perhaps even a pinto by leaving the cylinder and barrel in natural stainless and painting the frame matte black. Actually kinda looking forward to it! :-)