ΔE 17.0, loose: different enough that you should pick on purpose. Permanent Violet Dark is a little darker, more saturated, cooler than Warlock Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Permanent Violet Dark is a little darker, more saturated, cooler than Warlock Purple.
The same difference applies the other way round: Warlock Purple is a little lighter, more muted, 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 Purple on the colour wheel See Permanent Violet Dark on the colour wheel
All matches: Warlock Purple equivalents · Permanent Violet Dark equivalents