From Westcliffe, head south out of town on SH69 as though going to the South Colony Lakes area by the Crestones. Drive 4.4 miles south from the intersection of highways 69 and 96 in town, then turn right onto CR119 (Colfax Lane) and drive 5.5 miles to the junction where if you turn right, you'd be heading for the Crestones and South Colony Lakes. But instead of turning right, turn left, to the east, then in a few hundred yards, (quarter mile) the road again turns abruptly south and in about 5 miles comes to a trailhead parking area where passenger cars should give it up. This is the Rainbow trailhead here. Coordinates for this lower parking area at 9300 ft. are: N37° 55' 49.07" W 105° 27' 26.52".
If you have 4WD with good clearance, then proceed up the steepening 4WD road to the south and west for another 2.5 miles (appx.) to the upper trailhead at the coordinates and elevation given above. Our first drive up this road in 1995 was made in a Jeep Cherokee Sport. We found the road in surprisingly good shape, even though it was a steep single-track type road. In 2005 we returned to the same area in a Toyota T-100 pickup. In those 10 intervening years, the road condition had deteriorated considerably. It proved more of a challenge in our longer-bed vehicle, but we still made it okay. In any event, be prepared for a rough ride on a steep, narrow road with difficult rocky stretches. Reaching this upper parking area will greatly shorten the suggested backpack.
Primitive camping is available at both the upper and lower trailheads. There are no close by National Forest Service campgrounds.