Lothern Blue vs Amarth Blue

How close are they?

ΔE 6.6, close: similar, with a visible difference side by side. Amarth Blue is more saturated, warmer than Lothern Blue.

Can I use Amarth Blue instead of Lothern Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Amarth Blue is more saturated, warmer than Lothern Blue.

Can I use Lothern Blue instead of Amarth Blue?

The same difference applies the other way round: Lothern Blue is more muted, 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.