ΔE 18.5, loose: different enough that you should pick on purpose. Ground Brown is much more muted, cooler than Catachan Flesh.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Ground Brown is much more muted, cooler than Catachan Flesh.
The same difference applies the other way round: Catachan Flesh is much more saturated, 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 Catachan Flesh on the colour wheel See Ground Brown on the colour wheel
All matches: Catachan Flesh equivalents · Ground Brown equivalents