Amethyst Blue vs Corvus Black

How close are they?

ΔE 16.6, loose: different enough that you should pick on purpose. Corvus Black is a little darker, much more muted than Amethyst Blue.

Can I use Corvus Black instead of Amethyst Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Corvus Black is a little darker, much more muted than Amethyst Blue.

Can I use Amethyst Blue instead of Corvus Black?

The same difference applies the other way round: Amethyst Blue is a little 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.