Black Ink vs Ink Black Green

How close are they?

ΔE 16.6, loose: different enough that you should pick on purpose. Ink Black Green is noticeably lighter, more saturated than Black Ink.

Can I use Ink Black Green instead of Black Ink?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Ink Black Green is noticeably lighter, more saturated than Black Ink.

Can I use Black Ink instead of Ink Black Green?

The same difference applies the other way round: Black Ink 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.