ΔE 46.4, loose: different enough that you should pick on purpose. Ink Black Green is noticeably darker, much more muted, warmer than Piggy Purple Ink.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 46). Ink Black Green is noticeably darker, much more muted, warmer than Piggy Purple Ink.
The same difference applies the other way round: Piggy Purple Ink is noticeably lighter, much 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 Piggy Purple Ink on the colour wheel See Ink Black Green on the colour wheel
All matches: Piggy Purple Ink equivalents · Ink Black Green equivalents