We've spent 1 night at Colonial Creek on a few different occasions but this is never our final destination. This is nothing against the campground, its been good to us so far. Always acceptably clean and we've always managed to find camp sights with little to no view of the neighboring camp. We've never managed to snag a lake location but they seem a bit more close and snugly than the other sites anyways. There are a number of the sites we deem "normal' just off the main or center loops but we typically keep along the back of the loop along the forest where there are more private, wooded sites and walk-in camp sites available.
We tend to use this campground as a starting point to either go backpacking up the Thunder Creek trail, the trail-head is located in the back of the campground near the amphitheater or to boat into campsites off Lake Diablo, the boat-launch is located at the front of the campground near the ranger booth.
Though after reading a few other reviews of this campground on this website we are planning a group trip back this winter in hopes of some astrophtography shots over the frozen lake.
A worthy side trip just a few minutes past the campground is the Lake Diablo overlook, well worth the trip for the view.