pitch black vs ebony

pitch black and ebony both are nouns.

Word	Noun	Adjective	Verb	Adverb
pitch black	Yes	No	No	No
ebony	Yes	Yes	No	No

As nouns, pitch black and ebony are synonyms defined as:

Other synonyms of pitch black include coal black, jet black, sable, soot black.

pitch black (noun)	ebony (noun)
a very dark black	a very dark black
	tropical tree of southern Asia having hard dark-colored heartwood used in cabinetwork
	hard dark-colored heartwood of the ebony tree; used in cabinetwork and for piano keys

pitch black (adjective)	ebony (adjective)
	of a very dark black