ΔE 24.3, loose: different enough that you should pick on purpose. Vampiric Purple is a little darker, cooler than Garnet Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Vampiric Purple is a little darker, cooler than Garnet Purple.
The same difference applies the other way round: Garnet Purple is a little 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 Garnet Purple on the colour wheel See Vampiric Purple on the colour wheel
All matches: Garnet Purple equivalents · Vampiric Purple equivalents