The colour combination of the flags on both birds is white over yellow above the knee on the right leg.
This is the combination used in Hong Kong - both birds have been ringed locally at Mai Po.
The combination for Korea is white over orange. Unfortunately the yellow flag from HK can at times become slightly stained and looks a bit darker than usual. The presence of staining is usually fairly apparent if you check carefully, for example uneven colour or a darkening of the white flag as well.
Orange flags should stand out as a different colour - check through the flocks of stints and curlew sandpipers, which often include orange-flagged birds, to become more familiar with true colour of these flags.
