ΔE 6.4, 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 6). 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 Barley Gray BS4800/18B21 on the colour wheel See Dark Ghost Gray on the colour wheel
All matches: Barley Gray BS4800/18B21 equivalents · Dark Ghost Gray equivalents