red-gray vs reddish-grey

red-gray and reddish-grey both are adjectives.

Word	Noun	Adjective	Verb	Adverb
red-gray	No	Yes	No	No
reddish-grey	No	Yes	No	No

As adjectives, red-gray and reddish-grey are synonyms defined as:

Other synonyms of red-gray include red-grey, reddish-gray.

red-gray (adjective)	reddish-grey (adjective)
of grey tinged with red	of grey tinged with red