ΔE 13.1, fair: the same colour family, but not a straight swap. Dark Plum is noticeably darker, cooler than Grimoire Purple.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Dark Plum is noticeably darker, cooler than Grimoire Purple.
The same difference applies the other way round: Grimoire Purple 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 Grimoire Purple on the colour wheel See Dark Plum on the colour wheel
All matches: Grimoire Purple equivalents · Dark Plum equivalents