ΔE 13.2, fair: the same colour family, but not a straight swap. Ratskin Flesh is noticeably lighter, more muted than Rust.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Ratskin Flesh is noticeably lighter, more muted than Rust.
The same difference applies the other way round: Rust is noticeably darker, 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 Ratskin Flesh on the colour wheel
All matches: Rust equivalents · Ratskin Flesh equivalents