Burn Orange vs Orange Rust

How close are they?

ΔE 8.7, close: similar, with a visible difference side by side. Orange Rust is a little darker, more muted than Burn Orange.

Can I use Orange Rust instead of Burn Orange?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Orange Rust is a little darker, more muted than Burn Orange.

Can I use Burn Orange instead of Orange Rust?

The same difference applies the other way round: Burn Orange is a little lighter, 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.