ΔE 14.1, fair: the same colour family, but not a straight swap. Doom Metal is noticeably darker than Canoptek Alloy.
Can I use Doom Metal instead of Canoptek Alloy?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Doom Metal is noticeably darker than Canoptek Alloy.
Can I use Canoptek Alloy instead of Doom Metal?
The same difference applies the other way round: Canoptek Alloy 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.