ΔE 20.0, loose: different enough that you should pick on purpose. Amethyst is noticeably darker, much more saturated than Tentacle Pink.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Amethyst is noticeably darker, much more saturated than Tentacle Pink.
The same difference applies the other way round: Tentacle Pink is noticeably lighter, much more muted.
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 Tentacle Pink on the colour wheel See Amethyst on the colour wheel
All matches: Tentacle Pink equivalents · Amethyst equivalents