I am using SonarQube health check API. Need info on status RED and YELLOW

I am using SonarQube community edition 8.6 version and I am preparing documentation on SonarQube Health check (http://localhost:9000/api/system/health). I have referred to your documentation but it could not solve my below queries:

  1. What status does Yellow and Red mean?
  2. In what scenario do the above statuses occur?