ΔE 29.1, loose: different enough that you should pick on purpose. Permanent Violet Dark is noticeably darker, much more saturated, cooler than Fairy Pink.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Permanent Violet Dark is noticeably darker, much more saturated, cooler than Fairy Pink.
The same difference applies the other way round: Fairy Pink is noticeably lighter, much 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 Fairy Pink on the colour wheel See Permanent Violet Dark on the colour wheel
All matches: Fairy Pink equivalents · Permanent Violet Dark equivalents