ΔE 15.2, loose: different enough that you should pick on purpose. Mahogany is a little darker, more muted, warmer than Grimoire Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Mahogany is a little darker, more muted, warmer than Grimoire Purple.
The same difference applies the other way round: Grimoire Purple is a little lighter, more saturated, 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 Mahogany on the colour wheel
All matches: Grimoire Purple equivalents · Mahogany equivalents