Brought my quad elk hunting the last two years and I have decided its not worth the effort. I legally ran around on forest roads two days before the season opened, parked it at camp on Friday night and loaded it up the following Wednesday afternoon. (located areas of interest, parked it and did a lot of scouting using my boots) Will not bring it for this years hunt. Just not worth the effort and extra gas it takes to bring it in the area I hunt in.
Depending on the area you are going to in Colorado, it may be best to leave your ATV at home. If you decide to bring it with you, the Colorado OHV tag is easy to obtain and only costs $15. They send it the day after you order it and it's good for a year (March to March) You ordered it from the Parks & Recreation website which a link can be found on the CDOW site under the OHV information.
My $0.02 264X300