ΔE 26.9, loose: different enough that you should pick on purpose. Amethyst is a little lighter, much more saturated, warmer than Pastel Violet.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Amethyst is a little lighter, much more saturated, warmer than Pastel Violet.
The same difference applies the other way round: Pastel Violet is a little darker, much more muted, 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 Pastel Violet on the colour wheel See Amethyst on the colour wheel
All matches: Pastel Violet equivalents · Amethyst equivalents