silver-gray hair; salt-and-pepper hair
Refers specifically to the attractive, distinguished gray hair often associated with middle-aged or older men. A wasei-eigo term from 'romance gray'.
wasei-eigo (Japanese-coined English), from romance gray
His silver-gray hair is really attractive.
Lately, some young people seem to admire silver-gray hair.
handsome gray-haired man; silver fox
By extension, a good-looking man with gray or silver hair, often implying mature charm. The English 'silver fox' is a close equivalent.
That actor has really become a handsome gray-haired man, hasn't he?
He's more attractive now as a silver fox than when he was young.