ΔE 9.3, close: similar, with a visible difference side by side. Alien Purple is a little darker, warmer than Violet.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Alien Purple is a little darker, warmer than Violet.
The same difference applies the other way round: Violet is a little lighter, 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 Violet on the colour wheel See Alien Purple on the colour wheel
All matches: Violet equivalents · Alien Purple equivalents