ΔE 12.1, fair: the same colour family, but not a straight swap. Gorgon Brown is a little lighter, more muted, warmer than Rust.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Gorgon Brown is a little lighter, more muted, warmer than Rust.
The same difference applies the other way round: Rust is a little darker, more saturated, 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 Rust on the colour wheel See Gorgon Brown on the colour wheel
All matches: Rust equivalents · Gorgon Brown equivalents