Rusty Brass vs Gold Brown

How close are they?

ΔE 15.6, loose: different enough that you should pick on purpose. Gold Brown is noticeably lighter, cooler than Rusty Brass.

Can I use Gold Brown instead of Rusty Brass?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Gold Brown is noticeably lighter, cooler than Rusty Brass.

Can I use Rusty Brass instead of Gold Brown?

The same difference applies the other way round: Rusty Brass is noticeably darker, 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.