Emperor Gold vs Grave Robber

How close are they?

ΔE 21.4, loose: different enough that you should pick on purpose. Grave Robber is much more muted, cooler than Emperor Gold.

Can I use Grave Robber instead of Emperor Gold?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Grave Robber is much more muted, cooler than Emperor Gold.

Can I use Emperor Gold instead of Grave Robber?

The same difference applies the other way round: Emperor Gold is much more saturated, 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.