A little backcountry for a lot of solitude
Easy access off the main highway makes the main camping of this area accessible for any car that can handle the 9600 ft altitude. Clearly equipped to be family-friendly with designated camping plots and basic amenities like toilets. The lake is lovely, and with hiking trail access to more than one trail, it offers fishing, hiking, and of course relaxing. This place is popular, however, so you may elect to go the more secluded route.
A 4WD access road exists soon after the main entrance to the rainbow lakes campground. As of June 2016 it is closed. That's because water levels have made parts of the road inaccessible. But if you want a more secluded and unbelievable experience, hike in. It's 1.5 miles on a 4WD road that has parts that will see you walk ankle deep in water. Yes, you can avoid it by simply walking in the woods around these large puddles, but at .4 miles into the whole hike there's a knee deep (I'm 5'9") slow current river you're going to have to wade through, so your shoes will be wet anyway, so might as well. Warm the shoes by the campfire :-) When you reach camp, there are more than 30 campsite spots, and spread out. Id be shocked if it was full ever. I was the only one there that night. And they're real campsites with cleared space and fire pits. Naturally well shaded too.
At this camp, you're close to a river for fishing. You can easily hike around too. Or chill.
Its a bit of a workout to get there, but w packing properly and toughing a water wade, the seclusion will be well worth it for those looking for a little for quiet or looking to best the family crowds. There are moose in the area. Saw two during the one day stay there.
Remember, regardless of where you stay, you're at almost 10,000 ft elevation so at night, you'll be cold without some layered clothing options and a proper sleeping bag..