ΔE 6.5, close: similar, with a visible difference side by side. Our swatches for the two are almost the same.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). The swatches are almost the same.
The same difference applies the other way round.
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 Dark Seagray BS381C/638 on the colour wheel See Dark Grey Blue on the colour wheel
All matches: Dark Seagray BS381C/638 equivalents · Dark Grey Blue equivalents