Hello John,
Thanks for the identification, this helps.
I've thought about the possibility of this bird was a Starling juvenile. And I wondered would that be two plumage phases of the Black-collared Starling juvenile? I'd only seen the beige head colour plumage of the Black-collared Starling juvenile before.
Another fact was I heard this bird called like a Starling when it flew away. If this were a Common Myna, could it imitate the call of a Starling or I'd heard wrong.