ΔE 7.2, close: similar, with a visible difference side by side. USAF Brown is a little lighter, more saturated than Ancient Forest.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). USAF Brown is a little lighter, more saturated than Ancient Forest.
The same difference applies the other way round: Ancient Forest is a little darker, more muted.
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 Ancient Forest on the colour wheel See USAF Brown on the colour wheel
All matches: Ancient Forest equivalents · USAF Brown equivalents