1. I could not find any definitive information for this route, so I basically hiked it using the limited information I had, maps, and my own intuition. If there is a better route on this ridge that anyone is aware of, with an actual human-made trail for instance, please let me know or add your input to this page!
2. 'Bushwhacking' should be done with the utmost respect for the land you are on. Try to stay on trails (be they human or animal-made) to keep the outdoors as pristine as possible.
If you have only a regular 2WD vehicle, park at the South Colony Trailhead. If you have a good 4WD with high clearance and know how to use it, continue up the dirt (and rock and stone) road. The next 1.5 mile is privately-owned, so you must continue at least to the San Isabel National Forest Boundary. There are several places to pull off and camp after this point. You do not want to continue too far past the National Forest Boundary, because the well-marked Rainbow Trail, which you want to use, crosses the road less than a half mile later.
The Rainbow Trail is marked with a large brown metal sign and is impossible to miss, especially if you are looking for it. Turn right (north) onto this trail and follow it to South Colony Creek. Cross the sturdy wooden bridge there and continue to follow the trail as it makes a large turn around the jutting ridge. Then you will begin a steady but gradual downhill toward the next basin. This section of the Rainbow Trail is very straight.
After about three-quarters of a mile total on the Rainbow Trail, you will come to an old but obvious dirt road (GPS coords: N37deg59.228' W105deg30.281'). At only about 9,800 feet, the uphill is about to begin.
Follow the dirt road straight up the hillside. There are a few logs you have to step over, but other than that this is a very nice road to follow and you gain elevation quickly. Eventually though, it fizzles into a game trail. Here is where the bushwhacking begins. There are plenty of deer and elk trails to follow. Continue using them in your upward progress. Eventually you should end up coming to 'the top,' where the ridge flattens out somewhat. Try to stay on the south side of this ridge as you turn west and head uphill again. The south side is generally more gradual than the north side of this ridge.
The walking may be fairly steep at times, but there there are very few obstacles (logs, etc.) along this pleasant ridge. Timberline is at about 11,500 feet. Once you break out of that you should be able to see the first false summit of Humboldt above you. Work your way up the tundra to this 13,000 foot spot (see provided photograph), then continue along the ridgeline westward.
Once at the 13,000 foot false summit, the walking is very gradual for the most part. I'm not sure of the exact distance, but it is still a pretty good clip to the summit. Most of it is easy walking, and the last several hundred feet of elevation gain are on moderately steep talus, as with most fourteeners. I did not happen to notice any cairns or even a human-made trail my entire way from the Rainbow Trail to the summit, but once you get above timberline, where to go is pretty self-explanatory. Up!
BEWARE: There are steep dropoffs on the north side of the ridge, whether you are approaching the summit from the west or the east. Be careful to avoid these by hiking along the ridge-line or slightly on the south side of the ridge.
GPS highly recommended! As usual, take lots of water and anything else you should normally have along for a hike in Colorado.