ΔE 27.8, loose: different enough that you should pick on purpose. Brown Grey Wash is a little darker, much more muted than Reikland Fleshshade.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 28). Brown Grey Wash is a little darker, much more muted than Reikland Fleshshade.
The same difference applies the other way round: Reikland Fleshshade is a little lighter, much 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 Reikland Fleshshade on the colour wheel See Brown Grey Wash on the colour wheel
All matches: Reikland Fleshshade equivalents · Brown Grey Wash equivalents