How long the health code will change color is related to the environment you experience. If you are always in a safe environment, your health code will never change color. If you come into contact with patients in COVID-19, your health code will change from green to yellow or red. After discoloration, it must be isolated and tested for nucleic acid. Only when the nucleic acid test is negative for more than three times and the isolation time is more than 14 days can we change back to the green code through community application.