Quicksilver vs Brassy Brass

How close are they?

ΔE 22.4, loose: different enough that you should pick on purpose. Brassy Brass is noticeably darker, more saturated than Quicksilver.

Can I use Brassy Brass instead of Quicksilver?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Brassy Brass is noticeably darker, more saturated than Quicksilver.

Can I use Quicksilver instead of Brassy Brass?

The same difference applies the other way round: Quicksilver is noticeably lighter, more muted.

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.