If your health code and travel code are green, it is normal. The QR code scans the yellow code, so this situation should be that you have not done nucleic acid testing. As long as you have done a nucleic acid test, it will turn into a green code.
The reason why the green code becomes the yellow code is because the health code has moved and stayed near the key places where the confirmed cases and asymptomatic infected people have stayed, and may have had contact with the confirmed cases and asymptomatic infected people, so it is included in the scope of the yellow code.