Deep Amethyst vs Violet

How close are they?

ΔE 8.9, close: similar, with a visible difference side by side. Violet is a little lighter, more muted, warmer than Deep Amethyst.

Can I use Violet instead of Deep Amethyst?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Violet is a little lighter, more muted, warmer than Deep Amethyst.

Can I use Deep Amethyst instead of Violet?

The same difference applies the other way round: Deep Amethyst 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.