Diabolic Plum vs Liche Purple

How close are they?

ΔE 7.4, close: similar, with a visible difference side by side. Liche Purple is more muted than Diabolic Plum.

Can I use Liche Purple instead of Diabolic Plum?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Liche Purple is more muted than Diabolic Plum.

Can I use Diabolic Plum instead of Liche Purple?

The same difference applies the other way round: Diabolic Plum is more saturated.

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.