The camera is one of the main reasons I purchased an HTC One (M7), with its awesome low-light performance, so I was really bummed when my pictures started getting a weird purple tint around the edges. The problem got progressively worse, to the point that the camera was essentially unusable:
In my case, I went down to the local Sprint affiliate and inquired about a camera replacement. The tech started an insurance report and found that 'camera takes purple pictures' was one of the pre-defined claims, so he was able to order a refurbished phone for me on the spot at no cost (not even an insurance deductible!). A couple days later, I received my new phone and its camera works as well as I remembered. I'll update this post if it starts showing the same issues.