ΔE 11.7, fair: the same colour family, but not a straight swap. Russian AF Grey N.4 is a little lighter, more saturated, cooler than Bright Brown Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Russian AF Grey N.4 is a little lighter, more saturated, cooler than Bright Brown Grey.
The same difference applies the other way round: Bright Brown Grey is a little darker, 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 Bright Brown Grey on the colour wheel See Russian AF Grey N.4 on the colour wheel
All matches: Bright Brown Grey equivalents · Russian AF Grey N.4 equivalents