Runic Gold vs Gold Brown

How close are they?

ΔE 21.6, loose: different enough that you should pick on purpose. Gold Brown is noticeably lighter, more muted, warmer than Runic Gold.

Can I use Gold Brown instead of Runic Gold?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Gold Brown is noticeably lighter, more muted, warmer than Runic Gold.

Can I use Runic Gold instead of Gold Brown?

The same difference applies the other way round: Runic Gold is noticeably darker, 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.