I don't live in CO, but I've ride there every other year. It'll be down on power and you'll want/need the high altitude plug (I've wired mine to a switch on the dash).
I've ridden two-up with my, then, 15 y/o son without issues. Passing is near impossible at 10k feet but you'll be able to keep up with traffic, no problem.
I've also climbed Pikes Peak (14,100 ft) on my k75rt without issues.
There is a lot of great riding in CO. US-550 comes to mind.
Tom