Ebony is a very black tree. it is the color of the black keys on
Ebony, (there are several species of trees of the genus Diospyros
(family Ebenaceae), is a hardwood that is dark reddish-brown to
almost black in colour. Gaboon ebony wood is the most pure black of
the them all.
Alas black is the darkest of the dark, very-est of the very.
There is no other colour darker beyond the pitch of black.
Therefore, the answer in which you seek is black.
Unless, if you mean other descriptive words for it I have a few
on mind: Ebony, Midnight, Jet, Charcoal, Ink, etc.