Interesting. This looks very like a bird I saw back in April 2006 on Tung Ping Chau. That record is still in circulation with the Records Committee.
The pattern of the underparts does not favour Hainan Blue, which should have a blue breast. I had wondered at the time of my record whether first year Hainan Blue may show a different pattern, but I now know that this is not the case, and that Hainan Blue reaches adult-like plumage (i.e. with the blue breast) after post-juvenile moult.
The pale orange of the underparts also does not favour Chinese Blue Flycatcher (glaucicomans) which is on Cat. B of the HK list, and is often considered a subspecies of Blue-throated. The pale orange is suggestive of subspecies klossi of Blue-throated. In addition to my bird, I know that individuals seen in TPK last year were thought to have features suggesting klossi. The problem is that klossi is supposedly a resident species occurring no closer than southern Vietnam.
I believe the Records Committee currently consider these records to relate to individuals (probably glaucicomans) with a captive origin which have been fed on a poor diet. I find it interesting, though, that there have been a few such records in the past few years. Personally I suspect these actually are klossi, but acknowledge that this does not fit with the existing known distribution.
Vivian, please remember to submit this record to the Records Committee so that it can be properly assessed.
