ΔE 11.2, fair: the same colour family, but not a straight swap. Field Green-Grey is a little darker, warmer than Waaagh! Flesh.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Field Green-Grey is a little darker, warmer than Waaagh! Flesh.
The same difference applies the other way round: Waaagh! Flesh is a little lighter, cooler.
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 Waaagh! Flesh on the colour wheel See Field Green-Grey on the colour wheel
All matches: Waaagh! Flesh equivalents · Field Green-Grey equivalents