ΔE 29.4, loose: different enough that you should pick on purpose. Amethyst Purple is noticeably darker, much more saturated, cooler than Orchid Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Amethyst Purple is noticeably darker, much more saturated, cooler than Orchid Purple.
The same difference applies the other way round: Orchid Purple 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 Orchid Purple on the colour wheel See Amethyst Purple on the colour wheel
All matches: Orchid Purple equivalents · Amethyst Purple equivalents