Alien Purple vs Violet Vamp

How close are they?

ΔE 8.9, close: similar, with a visible difference side by side. Violet Vamp is a little darker than Alien Purple.

Can I use Violet Vamp instead of Alien Purple?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Violet Vamp is a little darker than Alien Purple.

Can I use Alien Purple instead of Violet Vamp?

The same difference applies the other way round: Alien Purple is a little lighter.

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.