Ruddy Terra vs Rust in Peace

How close are they?

ΔE 8.5, close: similar, with a visible difference side by side. Rust in Peace is a little lighter, more muted than Ruddy Terra.

Can I use Rust in Peace instead of Ruddy Terra?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Rust in Peace is a little lighter, more muted than Ruddy Terra.

Can I use Ruddy Terra instead of Rust in Peace?

The same difference applies the other way round: Ruddy Terra is a little darker, more saturated.

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.