ΔE 18.9, loose: different enough that you should pick on purpose. Mechanicus Standard Grey is a little darker, much more muted than Demon Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Mechanicus Standard Grey is a little darker, much more muted than Demon Purple.
The same difference applies the other way round: Demon Purple is a little lighter, much more saturated.
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 Demon Purple on the colour wheel See Mechanicus Standard Grey on the colour wheel
All matches: Demon Purple equivalents · Mechanicus Standard Grey equivalents