ΔE 33.5, loose: different enough that you should pick on purpose. Medium Magenta is noticeably lighter, more saturated, warmer than Genestealer Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 33). Medium Magenta is noticeably lighter, more saturated, warmer than Genestealer Purple.
The same difference applies the other way round: Genestealer Purple is noticeably darker, more muted, 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 Genestealer Purple on the colour wheel See Medium Magenta on the colour wheel
All matches: Genestealer Purple equivalents · Medium Magenta equivalents