ΔE 9.4, close: similar, with a visible difference side by side. Waaagh! Flesh is a little darker, warmer than Green Hell.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Waaagh! Flesh is a little darker, warmer than Green Hell.
The same difference applies the other way round: Green Hell 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 Green Hell on the colour wheel See Waaagh! Flesh on the colour wheel
All matches: Green Hell equivalents · Waaagh! Flesh equivalents