There are no blued revolvers manufactured in 500 S&W. The Smith in stainless is probably the best. Taurus makes a 500 as I recall. The BFR comes in 500 also, but it is a single action.
If Ruger ever comes out with a 500 it will also likely be in stainless steel. I can't see it happening, but you never know. The Super Redhawk in 480 Ruger has not been highly successful. I have one. They are available in 7.5 and 9.5" models. The 454 Casul version seems to be more popular with buyers. It's a handfull to shoot and I have little need or desire to own a 500 S&W. By the way, the 480 Ruger is a very good caliber and you'd probably be very happy with it vs a 500. It also is a stainless DA revolver.