A quick note: I rated this 4 stars because I prefer back country/dispersed camping over campgrounds. Given the potential difficulty of the hike and other factors, some might rate this much lower.
First and foremost, I had a black bear encounter at this location. Make sure that you remain bear aware and are taking the appropriate safety measures. You're required to have a bear-proof container when camping in this area and you can find some for rent on your drive in.
There are a couple of ways to get to Lake Colden but I parked at the Upper Works Trailhead and took Calamity Brook Trail past the flowed lands, across the dam, and to the campground. All said, it was approx. 6 miles in.
You've got a couple of options when camping in this area. There are lean-tos available, but if you hike in expecting to get one you're at the mercy of your own luck--they might already be occupied. Otherwise, there are sites near Lake Colden with a short walk to a river to collect water or relax in nearby.
The sites are primitive to say the least, but are near a ranger station. The rangers I met were nice, friendly and willing to provide recommendations of hikes to take in the area. They also dispensed up to date information about local bear sightings. The sites are dispersed and there are toilets located in the area; however, they're in the middle of nowhere so don't expect the nicest bathroom you've ever been in. Speaking of the middle of nowhere, there's no cell service. Fires are prohibited so you'll have to rely on a camp stove for cooking, and you'll need to be wary of weather that has a habit of changing quickly.
A major benefit of camping here sets you up for a couple of potential day hikes if you'd like, and willingness or ability to accomplish most will be based on your own personal comfort or fitness. From Lake Colden, if you'd like to bag some peaks you can hike Mt. Colden, Mt. Skyline, the backside of Mt. Marcy, or Algonquin Peak. A word of caution, I'm in relatively good shape and I found some of these hikes quite strenuous.