I remember watching an Asian horror movie (possibly from Hong Kong?) some time between 2010 and now. It was not older than 5 years by that time, I think.
The movie repeatedly featured a ghost that appeared as a young woman whose arms were noticeably dark blue from the elbows down. The revelation in the end was that the woman was one of many workers in an underground sweatshop (for dyeing fabrics or something - hence the blue arms) who overheard a secret conversation between the owners of said sweatshop, was discovered, and murdered by getting an axe smashed into her head.
At least a few of these aspects are probably misremembered, because my otherwise quite reliable google-fu does not seem to help here.