Dark Highlights vs Rust

How close are they?

ΔE 8.7, close: similar, with a visible difference side by side. Rust is a little lighter, more muted, cooler than Dark Highlights.

Can I use Rust instead of Dark Highlights?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Rust is a little lighter, more muted, cooler than Dark Highlights.

Can I use Dark Highlights instead of Rust?

The same difference applies the other way round: Dark Highlights is a little darker, more saturated, warmer.

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.