Rust Brown vs Faded Red

How close are they?

ΔE 8.0, close: similar, with a visible difference side by side. Faded Red is a little lighter, more saturated than Rust Brown.

Can I use Faded Red instead of Rust Brown?

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

Can I use Rust Brown instead of Faded Red?

The same difference applies the other way round: Rust Brown is a little darker, more muted.

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.