ΔE 9.8, close: similar, with a visible difference side by side. Extra Dark Seagray BS381C 640 is a little darker, more saturated, cooler than Deep Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Extra Dark Seagray BS381C 640 is a little darker, more saturated, cooler than Deep Grey.
The same difference applies the other way round: Deep Grey is a little lighter, more muted, 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.
See Deep Grey on the colour wheel See Extra Dark Seagray BS381C 640 on the colour wheel
All matches: Deep Grey equivalents · Extra Dark Seagray BS381C 640 equivalents