ΔE 6.4, close: similar, with a visible difference side by side. Grey Blue is warmer than Extra Dark Seagray BS381C 640.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). Grey Blue is warmer than Extra Dark Seagray BS381C 640.
The same difference applies the other way round: Extra Dark Seagray BS381C 640 is 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.
See Extra Dark Seagray BS381C 640 on the colour wheel See Grey Blue on the colour wheel
All matches: Extra Dark Seagray BS381C 640 equivalents · Grey Blue equivalents