Yes, both Great Knot. Both flagged in western Australia (yellow flag). These are excellent observations - I have been looking unsuccessfully for colour ringed birds passing through Hong Kong.
A couple of minor comments on the ring combinations:
Bird 1. I think the left leg combination is actually Yellow, Red, Green. I realise the green is not very obvious on this bird, but I think that is due to the light. It is also important to note that this is a yellow flag, not a colour ring (also very important to note that this is on the lower leg). This bird is part of an ongoing study in Australia and China looking into refuelling behaviour by Great Knot, Red Knot and Bar-tailed Godwit.
Bird 2. I think the Australian combinations only use letters, not numbers. I think the combination on this bird is UZD, but it's not too clear due to distance (and possibly also the flag has faded slightly).
It is worth reporting both birds to the Australian Wader Study Group, who will be able to provide more information on when/where these birds were ringed (and resighted). Author: tsawong Time: 26/04/2011 23:07
Thanks to Ronaldo for ID.
Also thanks to ajohn. You are right, the first bird is ringed as Yellow, Red and Green while the second one is flagged UZD after more processing on the photos. You have very sharp eyes.
I took the liberty of reporting these flag sightings to the AWSG (along with other flag sightings I had this weekend), and have the following information in return.
Great Knot 3RLBB (the colour-ringed bird) was first ringed on 29 August 2010 at Roebuck Bay, Broome, Western Australia. It has been resighted there three times until 19 March 2011.
Great Knot UZD was ringed 11 March 2011 at Roebuck Bay and has been resighted there twice until 16 April 2011 - only 8 days before this photograph at Mai Po.
I am especially pleased because I was actually present when UZD was ringed!