ΔE 9.8, close: similar, with a visible difference side by side. Amethyst Purple is a little lighter, more muted, warmer than Alien Purple. They are different kinds of paint: Army Painter Alien Purple is an opaque base/layer paint and Green Stuff World Amethyst Purple is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Amethyst Purple is a little lighter, more muted, warmer than Alien Purple. They are different kinds of paint.
The same difference applies the other way round: Alien Purple is a little darker, 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 Alien Purple on the colour wheel See Amethyst Purple on the colour wheel
All matches: Alien Purple equivalents · Amethyst Purple equivalents