ΔE 9.1, close: similar, with a visible difference side by side. Light Rust is a little lighter, more saturated, cooler than Gorthor Brown.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Light Rust is a little lighter, more saturated, cooler than Gorthor Brown.
The same difference applies the other way round: Gorthor Brown is a little darker, more muted, 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 Gorthor Brown on the colour wheel See Light Rust on the colour wheel
All matches: Gorthor Brown equivalents · Light Rust equivalents