You can see pale pink legs and a pale tip to the bill - Pale-legged Leaf Warbler or Sakhalin Leaf Warbler (they cannot be told apart in the field). But they can be separated from all other phylloscopus warblers by these two features.
Other good features are the call - a high pitched "Pink", and they often pump the their tail up and down.
Cheers
Mike K
Mike KilburnVice Chairman, HKBWSChairman, Conservation Committee