I've been slowly digitizing all of my discs and tapes and came across a Fall '87 Hollywood Squares episode with various game show hosts doing bumpers and reading questions. In Bob's case, it's to help with a tongue-twister.
The relevant part here is Bob Barker's pretape - which filmed during the summer '87 taping break - between Bob's last dark hair Price and first gray hair Price.
Bob wears a giant, utterly ridiculous cowboy hat to try to hide the surprise, but if you look at his temples or eyebrows (especially on his left / camera right) the dye is working its way out of his hair and the gray is shining through. And this aired a month (9/16/87) before he showed up Gray on Price. It's the dumbest thing, but the part that's most Price related (Bob's apperance, you can watch it in less time than it took you to read this) is linked here
