ΔE 6.1, close: similar, with a visible difference side by side. Black Grey is a little darker, more muted than Brown Liner.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). Black Grey is a little darker, more muted than Brown Liner.
The same difference applies the other way round: Brown Liner is a little lighter, 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.
See Brown Liner on the colour wheel See Black Grey on the colour wheel
All matches: Brown Liner equivalents · Black Grey equivalents