Rust Tone vs Red Wash

How close are they?

ΔE 34.5, loose: different enough that you should pick on purpose. Red Wash is noticeably lighter, more saturated, cooler than Rust Tone.

Can I use Red Wash instead of Rust Tone?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 34). Red Wash is noticeably lighter, more saturated, cooler than Rust Tone.

Can I use Rust Tone instead of Red Wash?

The same difference applies the other way round: Rust Tone is noticeably darker, more muted, 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.