red-grey vs reddish-gray

red-grey and reddish-gray both are adjectives.

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

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

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

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