ΔE 13.0, fair: the same colour family, but not a straight swap. Magnesium is noticeably darker than Stormhost Silver.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Magnesium is noticeably darker than Stormhost Silver.
The same difference applies the other way round: Stormhost Silver is noticeably 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.
See Stormhost Silver on the colour wheel See Magnesium on the colour wheel
All matches: Stormhost Silver equivalents · Magnesium equivalents