ΔE 17.2, loose: different enough that you should pick on purpose. Bruised Purple is noticeably darker, warmer than Warpfiend Grey.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Bruised Purple is noticeably darker, warmer than Warpfiend Grey.
The same difference applies the other way round: Warpfiend Grey is noticeably lighter, cooler.
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 Warpfiend Grey on the colour wheel See Bruised Purple on the colour wheel
All matches: Warpfiend Grey equivalents · Bruised Purple equivalents