ΔE 9.1, close: similar, with a visible difference side by side. Nocturna Shadow is a little darker than Bright Brown Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Nocturna Shadow is a little darker than Bright Brown Grey.
The same difference applies the other way round: Bright Brown Grey is a little lighter.
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 Bright Brown Grey on the colour wheel See Nocturna Shadow on the colour wheel
All matches: Bright Brown Grey equivalents · Nocturna Shadow equivalents