Brass vs Ruby Red

How close are they?

ΔE 22.1, loose: different enough that you should pick on purpose. Ruby Red is noticeably lighter, more saturated than Brass.

Can I use Ruby Red instead of Brass?

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

Can I use Brass instead of Ruby Red?

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