ΔE 19.1, loose: different enough that you should pick on purpose. Orange Rust is a little lighter, much more saturated than Idrian Flesh.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Orange Rust is a little lighter, much more saturated than Idrian Flesh.
The same difference applies the other way round: Idrian Flesh is a little darker, much 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 Idrian Flesh on the colour wheel See Orange Rust on the colour wheel
All matches: Idrian Flesh equivalents · Orange Rust equivalents