ΔE 11.2, fair: the same colour family, but not a straight swap. Brown Grey Wash is a little lighter, more muted than Agrax Earthshade.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Brown Grey Wash is a little lighter, more muted than Agrax Earthshade.
The same difference applies the other way round: Agrax Earthshade is a little darker, 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 Agrax Earthshade on the colour wheel See Brown Grey Wash on the colour wheel
All matches: Agrax Earthshade equivalents · Brown Grey Wash equivalents