Status icon on main GCE window to enable to check whether user's startup-script is successfully run or not.
Currently users have to click serial console of each instance after run the instance(s) which startup-script is configured, for example, jupyter server, flask, etc...
To overcome the lazy action, GCE always check user's startup-script running and show the color status icon on main window of GCE instance list, which explains it outputs error or not.
RED icon: error occur in user's startup-script
YELLOW icon: Warning occur in user's startup-script
BLUE icon: Successfully run!