Extra Dark Seagray BS381C 640 vs Field Blue

How close are they?

ΔE 6.3, close: similar, with a visible difference side by side. Field Blue is a little lighter, more muted than Extra Dark Seagray BS381C 640.

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

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Field Blue is a little lighter, more muted than Extra Dark Seagray BS381C 640.

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

The same difference applies the other way round: Extra Dark Seagray BS381C 640 is a little darker, 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.