ΔE 13.0, fair: the same colour family, but not a straight swap. Magmadroth Flame is more saturated, cooler 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 Magmadroth Flame is a one-coat contrast-style 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). Magmadroth Flame is more saturated, cooler than Matt Light Rust. They are different kinds of paint.
The same difference applies the other way round: Matt Light Rust is more muted, 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.
See Matt Light Rust on the colour wheel See Magmadroth Flame on the colour wheel
All matches: Matt Light Rust equivalents · Magmadroth Flame equivalents