gray-brown vs greyish-brown

gray-brown and greyish-brown both are adjectives.

Word	Noun	Adjective	Verb	Adverb
gray-brown	No	Yes	No	No
greyish-brown	No	Yes	No	No

As adjectives, gray-brown and greyish-brown are synonyms defined as:

Other synonyms of gray-brown include grayish-brown, grey-brown.

gray-brown (adjective)	greyish-brown (adjective)
of brown tinged with grey	of brown tinged with grey