ΔE 7.1, close: similar, with a visible difference side by side. Iron Hue is a little darker than Stormhost Silver.
Can I use Iron Hue instead of Stormhost Silver?
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Iron Hue is a little darker than Stormhost Silver.
Can I use Stormhost Silver instead of Iron Hue?
The same difference applies the other way round: Stormhost Silver is a little lighter.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.