ΔE 10.2, fair: the same colour family, but not a straight swap. Fuegan Orange is a little darker, more saturated than Rust. They are different kinds of paint: AMMO by Mig Rust is an opaque base/layer paint and Citadel Fuegan Orange is a wash/shade, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Fuegan Orange is a little darker, more saturated than Rust. They are different kinds of paint.
The same difference applies the other way round: 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.
See Rust on the colour wheel See Fuegan Orange on the colour wheel
All matches: Rust equivalents · Fuegan Orange equivalents