ΔE 29.3, loose: different enough that you should pick on purpose. Starship Steel is noticeably darker, more saturated than Magnesium.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Starship Steel is noticeably darker, more saturated than Magnesium.
The same difference applies the other way round: Magnesium is noticeably lighter, more muted.
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 Magnesium on the colour wheel See Starship Steel on the colour wheel
All matches: Magnesium equivalents · Starship Steel equivalents