You're right about this being an annual event - Is it Pale Blue or is it a Verditer?
And once again I'm going to be the one to swoop in and say that this is a female Verditer - structure looks typical for Verditer and females usually have a grey breast/grey lores, as shown on this bird. The tone of the blue is normal for Verditer I would say.
I'm not going to go too much through old ground on this because there has been considerable discussion in the past. See these two threads for discussion on separation of these two species:
http://www.hkbws.org.hk/BBS/view ... ;highlight=verditer
http://www.hkbws.org.hk/BBS/view ... ;highlight=verditer
