coal black vs sable

coal black and sable both are nouns.

Word	Noun	Adjective	Verb	Adverb
coal black	Yes	No	No	No
sable	Yes	Yes	No	No

As nouns, coal black and sable are synonyms defined as:

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

coal black (noun)	sable (noun)
a very dark black	marten of northern Asian forests having luxuriant dark brown fur
	a scarf (or trimming) made of sable
	an artist's brush made of sable hairs
	a very dark black
	the expensive dark brown fur of the marten

coal black (adjective)	sable (adjective)
	of a dark somewhat brownish black