Ryza Rust vs Ember Orange

How close are they?

ΔE 6.2, close: similar, with a visible difference side by side. Ember Orange is a little darker than Ryza Rust.

Can I use Ember Orange instead of Ryza Rust?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Ember Orange is a little darker than Ryza Rust.

Can I use Ryza Rust instead of Ember Orange?

The same difference applies the other way round: Ryza Rust is a little lighter.

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.