I am re-bluing a mosin-nagant 91-30 and I am using Perma Blue from WalMart.  When I got done bluing six coats on it yesterday I sprayed rem oil on it to lube it up and the bluing turned a bronish color.  Do I need to put some kind of sealent on the gun to prevent this?  Thanks.

btt

If you read the directions on the bottle(I'm sure you did) they state that you should rinse with cold water after leaving the Perma Blue on for @30 sec.  That is supposed to "cure/neutralize" it.  You do have to wipe/ spray oil on it afterward to prevent rust.  I found that you can only put so many "coats" of Perma Blue on before it starts removing your work.  I think about 4 or 5 seems to get the darkest bluing.  

You need to remember that this is Cold bluing, thus, it is not permanent.  I have not had it turn to a plum/bronze color before.  It could be the type of metal.  Does the bottle say "Plum"?  They do sell that type. Wiping/spraying oil on it will remove some of your work, and could be the cause of the plum coloring. Maybe try a different type of oil.  Cold bluing is really for small areas, not for rebluing entire guns, but I have done it before.  Just don't expect it to stay that dark blue for long.  Most of the time enough remains to give a well used, but cared for look.  One of my revolvers has some slight holster wear on several of its sharp edges and on the end of the barrel.  I can put cold blue on these areas each time I clean the gun, but each time I carry it in a holster it will wear away.  Good luck