ΔE 13.1, fair: the same colour family, but not a straight swap. Ryza Rust is a little lighter, more saturated than Matt Light Rust. They are different kinds of paint: AMMO by Mig Matt Light Rust is an ink, glaze or transparent paint and Citadel Ryza Rust is an opaque base/layer paint, 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 13). Ryza Rust is a little lighter, more saturated than Matt Light Rust. They are different kinds of paint.
The same difference applies the other way round: Matt Light Rust is a little darker, 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 Matt Light Rust on the colour wheel See Ryza Rust on the colour wheel
All matches: Matt Light Rust equivalents · Ryza Rust equivalents