Red tint from the Iron? Yellow from Cr? Depends on the SS alloy as to the Ni content.
Now think of this, that first implosion device was not a hydrogen bomb. It was a fission device, not a fusion device.
How much more would be vaporized totally with modern nukes? It may be that there would be no trace of the container, since the container is much smaller now than the original at White Sands and The yield is so much larger.