ΔE 9.3, close: similar, with a visible difference side by side. Light Rust is more saturated, cooler than Graveyard Earth.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Light Rust is more saturated, cooler than Graveyard Earth.
The same difference applies the other way round: Graveyard Earth is 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 Graveyard Earth on the colour wheel See Light Rust on the colour wheel
All matches: Graveyard Earth equivalents · Light Rust equivalents