Grave Robber vs Brass

How close are they?

ΔE 21.9, loose: different enough that you should pick on purpose. Brass is a little darker, more saturated, warmer than Grave Robber.

Can I use Brass instead of Grave Robber?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Brass is a little darker, more saturated, warmer than Grave Robber.

Can I use Grave Robber instead of Brass?

The same difference applies the other way round: Grave Robber is a little lighter, more muted, 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.