I figure if I ask "What's the best cold blue?"..y'all will tell me Oxpho blue..
Truth being..I ain't had all that good of luck with the stuff..will work on some guns..not worth a hoot on others.
I've had pretty fair luck with Van's myself..My father was a fan of 4440 blue(can you still get that stuff?)..If Van's won't stick..G96 paste or the old stinky Birchwood Casy 'Perma-blue' sometimes will.
That's been my experience anyhow..and I may have had a bogus bottle of Oxpho blue..'cause it never worked for me like everyone claimed it did for them.
So just what is your favorite..and most effective..longest lasting cold blue?