Nocturne Green vs Extra Dark Seagray BS381C/640

How close are they?

ΔE 7.6, close: similar, with a visible difference side by side. Extra Dark Seagray BS381C/640 is more muted than Nocturne Green.

Can I use Extra Dark Seagray BS381C/640 instead of Nocturne Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Extra Dark Seagray BS381C/640 is more muted than Nocturne Green.

Can I use Nocturne Green instead of Extra Dark Seagray BS381C/640?

The same difference applies the other way round: Nocturne Green 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.