ΔE 21.7, loose: different enough that you should pick on purpose. Flesh Wash is noticeably lighter, warmer than Rust Tone.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Flesh Wash is noticeably lighter, warmer than Rust Tone.
The same difference applies the other way round: Rust Tone is noticeably darker, cooler.
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 Tone on the colour wheel See Flesh Wash on the colour wheel
All matches: Rust Tone equivalents · Flesh Wash equivalents