ΔE 12.3, fair: the same colour family, but not a straight swap. Word Bearers Red is a little darker, more muted than Rust.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Word Bearers Red is a little darker, more muted than Rust.
The same difference applies the other way round: Rust is a little lighter, more saturated.
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 Word Bearers Red on the colour wheel
All matches: Rust equivalents · Word Bearers Red equivalents