Navy Blue vs Extra Dark Seagray BS381C/640

How close are they?

ΔE 8.9, close: similar, with a visible difference side by side. Extra Dark Seagray BS381C/640 is a little lighter, cooler than Navy Blue.

Can I use Extra Dark Seagray BS381C/640 instead of Navy Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Extra Dark Seagray BS381C/640 is a little lighter, cooler than Navy Blue.

Can I use Navy Blue instead of Extra Dark Seagray BS381C/640?

The same difference applies the other way round: Navy Blue is a little darker, warmer.

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.