ΔE 11.5, fair: the same colour family, but not a straight swap. Knight-Questor Flesh is a little darker, more muted, cooler than Rust.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Knight-Questor Flesh is a little darker, more muted, cooler than Rust.
The same difference applies the other way round: Rust is a little lighter, 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.
See Rust on the colour wheel See Knight-Questor Flesh on the colour wheel
All matches: Rust equivalents · Knight-Questor Flesh equivalents