Old Rust vs Gorgon Brown

How close are they?

ΔE 7.8, close: similar, with a visible difference side by side. Gorgon Brown is a little lighter, more saturated, cooler than Old Rust.

Can I use Gorgon Brown instead of Old Rust?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Gorgon Brown is a little lighter, more saturated, cooler than Old Rust.

Can I use Old Rust instead of Gorgon Brown?

The same difference applies the other way round: Old Rust 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.