ΔE 58.3, loose: different enough that you should pick on purpose. Atramentum Black is noticeably darker, much more muted than Biel-Tan Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 58). Atramentum Black is noticeably darker, much more muted than Biel-Tan Green.
The same difference applies the other way round: Biel-Tan 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.
See Biel-Tan Green on the colour wheel See Atramentum Black on the colour wheel
All matches: Biel-Tan Green equivalents · Atramentum Black equivalents