gray-haired vs grey-headed

gray-haired and grey-headed both are adjectives.

Word	Noun	Adjective	Verb	Adverb
gray-haired	No	Yes	No	No
grey-headed	No	Yes	No	No

As adjectives, gray-haired and grey-headed are synonyms defined as:

gray-haired and grey-headed: showing characteristics of age, especially having grey or white hair

Other synonyms of gray-haired include gray-headed, gray, grey-haired, grey, grizzly, hoar, hoary, white-haired.

gray-haired (adjective)	grey-headed (adjective)
showing characteristics of age, especially having grey or white hair	showing characteristics of age, especially having grey or white hair