grayish-black vs gray-black

grayish-black and gray-black both are adjectives.

Word	Noun	Adjective	Verb	Adverb
grayish-black	No	Yes	No	No
gray-black	No	Yes	No	No

As adjectives, grayish-black and gray-black are synonyms defined as:

Other synonyms of grayish-black include grey-black, greyish-black.

grayish-black (adjective)	gray-black (adjective)
of black tinged with grey	of black tinged with grey