Inktense Olive vs Ink Black

How close are they?

ΔE 23.7, loose: different enough that you should pick on purpose. Ink Black is noticeably darker, much more muted than Inktense Olive.

Can I use Ink Black instead of Inktense Olive?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Ink Black is noticeably darker, much more muted than Inktense Olive.

Can I use Inktense Olive instead of Ink Black?

The same difference applies the other way round: Inktense Olive 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.