Beartooth Pass in Wyoming is better known, but nearby Chief Joseph Scenic Byway is no slouch. Definitely scenic, but also terrific fun on motorcycle, with smooth pavement and open sweepers. But if you are in the neighbourhood, along with Yellowstone National Park and Beartooth Pass, CJSB is worth a visit.
Btw, this pic is from the homeward leg of my June 2015 Colorado trip.