Rust Tone vs Brown Wash

How close are they?

ΔE 20.3, loose: different enough that you should pick on purpose. Brown Wash is a little darker, much more muted, warmer than Rust Tone.

Can I use Brown Wash instead of Rust Tone?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Brown Wash is a little darker, much more muted, warmer than Rust Tone.

Can I use Rust Tone instead of Brown Wash?

The same difference applies the other way round: Rust Tone is a little lighter, much more saturated, 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.