Peacock vs Beetle Green

How close are they?

ΔE 21.6, loose: different enough that you should pick on purpose. Beetle Green is noticeably darker, warmer than Peacock.

Can I use Beetle Green instead of Peacock?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Beetle Green is noticeably darker, warmer than Peacock.

Can I use Peacock instead of Beetle Green?

The same difference applies the other way round: Peacock is noticeably lighter, 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.