Took a look through Endo & Kishida (1999) Day-Flying Moths: Chalcosiinae, Epicopeia and missed Chalcosia suffusa the first time round, thinking it might be a Soritia sp. Looked again, thought (because of the red thoracic collar) it must be a Chalcosia and placed it as suffusa. Yen Shen Horn has confirmed this identification.
so the photo is of ...
This is a much less common species in HK (and generally) than its congener, C. pectinicornis.