ΔE 11.8, fair: the same colour family, but not a straight swap. Cam. Black Green is noticeably lighter than Abaddon Black.
Can I use Cam. Black Green instead of Abaddon Black?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Cam. Black Green is noticeably lighter than Abaddon Black.
Can I use Abaddon Black instead of Cam. Black Green?
The same difference applies the other way round: Abaddon Black is noticeably darker.
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.