ΔE 12.1, fair: the same colour family, but not a straight swap. Chestnut Brown is a little lighter, warmer than Grimoire Purple.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Chestnut Brown is a little lighter, warmer than Grimoire Purple.
The same difference applies the other way round: Grimoire Purple is a little darker, 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 Grimoire Purple on the colour wheel See Chestnut Brown on the colour wheel
All matches: Grimoire Purple equivalents · Chestnut Brown equivalents