Ryza Rust vs Ochre Desert

How close are they?

ΔE 8.7, close: similar, with a visible difference side by side. Ochre Desert is a little darker, more saturated than Ryza Rust.

Can I use Ochre Desert instead of Ryza Rust?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Ochre Desert is a little darker, more saturated than Ryza Rust.

Can I use Ryza Rust instead of Ochre Desert?

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