ΔE 12.6, fair: the same colour family, but not a straight swap. Grey Knights Steel is noticeably lighter than Dark Aluminium.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Grey Knights Steel is noticeably lighter than Dark Aluminium.
The same difference applies the other way round: Dark Aluminium is noticeably darker.
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 Dark Aluminium on the colour wheel See Grey Knights Steel on the colour wheel
All matches: Dark Aluminium equivalents · Grey Knights Steel equivalents