ΔE 25.3, loose: different enough that you should pick on purpose. Martian Green is noticeably darker, much more saturated, cooler than Canoptek Alloy.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Martian Green is noticeably darker, much more saturated, cooler than Canoptek Alloy.
The same difference applies the other way round: Canoptek Alloy is noticeably lighter, much more muted, warmer.
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 Canoptek Alloy on the colour wheel See Martian Green on the colour wheel
All matches: Canoptek Alloy equivalents · Martian Green equivalents