ΔE 13.3, fair: the same colour family, but not a straight swap. Xereus Purple is noticeably darker, cooler than Warlock Magenta.
✓ Army Painter Fanatic conversion chart lists these two as equivalents.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Xereus Purple is noticeably darker, cooler than Warlock Magenta.
The same difference applies the other way round: Warlock Magenta is noticeably lighter, 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 Warlock Magenta on the colour wheel See Xereus Purple on the colour wheel
All matches: Warlock Magenta equivalents · Xereus Purple equivalents