That happened to my RIR girl a few days ago too, her face was almost completely black! Is your rooster acting normal? My hen was acting okay, and they eventually when away on their own.
He is acting very normal except maybe a bit lethargic I think because of the heat. Heat index has been over 100 for a week now. He still runs around and protects his girls, finds them food, calls for them, and of course does his manly thing.