If for any reason you need to remove a light from the system, select the light on the main screen and open its settings ( the cog icon). Then scroll all the way down and tap “Delete”. The light will blink and turn to warm white.

If the light is not connected and you cannot reach it from the main screen:

iOS: Open the Settings tab and select Lights, then select the light to delete.

Android: Open the menu, select Lights then select the light you want to delete.