ΔE 14.0, fair: the same colour family, but not a straight swap. Dark Rust is much more muted, cooler than Feral Brown.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Dark Rust is much more muted, cooler than Feral Brown.
The same difference applies the other way round: Feral Brown 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 Feral Brown on the colour wheel See Dark Rust on the colour wheel
All matches: Feral Brown equivalents · Dark Rust equivalents