Nothing I can do about it.Please, please to the developer, would be really great if you could take a look at this
ZenWifi devices like the XT12 have a special RGB LED that's used to display a coloured status based on the boot process, or the state of the connection to other nodes. The code that controls that particular LED is closed source and outside of my control. Your LED most likely gets turned on due to an event that causes the XT12 to update the status/colour of that LED.
You can try disabling it through the AiMesh page instead of the stealth setting on the Administration page to see if it makes any difference.