Notice the color of the tree. That happens in like in mid October or so.
Yeah the Canyon is way cool. But don't expect to go wandering around by yourself unless you have permission from the Tribe, and also a guide. There are tours that will take you in on the back of a deuce-and-a-half, which stop at some nice photo-op locations like the on shown here, but there are plenty of other nice views also that are difficult from a bouncing truck.
The nearest I ever came getting killed was standing on the rim during a thunderstorm. A bolt of lighting hit the steel rail about 10 feet ahead of me as I was walking up to it. It was really bright, and really loud. There's a moral there, I should have stayed in the car. Anyhoo, there are some nice views from the road that more or less snakes around the rim of the canyon. Just don't die for them.