Glittering Green vs Boiler Black

How close are they?

ΔE 45.0, loose: different enough that you should pick on purpose. Boiler Black is noticeably darker, much more muted than Glittering Green.

Can I use Boiler Black instead of Glittering Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 45). Boiler Black is noticeably darker, much more muted than Glittering Green.

Can I use Glittering Green instead of Boiler Black?

The same difference applies the other way round: Glittering Green is noticeably lighter, much more saturated.

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.