Eye of Terror vs Warlord Purple

How close are they?

ΔE 9.4, close: similar, with a visible difference side by side. Warlord Purple is a little darker than Eye of Terror.

Can I use Warlord Purple instead of Eye of Terror?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Warlord Purple is a little darker than Eye of Terror.

Can I use Eye of Terror instead of Warlord Purple?

The same difference applies the other way round: Eye of Terror 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.