If you want to challenge yourself, Colorado offers some of the gnarliest runs in the U.S. that you can find on inbounds terrain. Zoom in: Most ski resorts have a famous double-black diamond, experts-only ski run. But the Colorado resorts listed below boast the toughest runs in the state, according to experts. Telluride’s Senior’s: You’ll have to hike a narrow ridge line to the summit of the resort’s highest point, Palmyra Peak at 13,320 feet…