The blue light appears when the wireless headset is unplugged from the charging cable because the charging cable is equipped with an LED indicator to indicate the charging status. When the wireless headset is connected to the charging cable and starts charging, the LED indicator will emit blue light. At this time, the headset is charging until the charging is complete and the indicator is off. Therefore, the blue light is only an indication of the charging status and will not affect the use of wireless headphones.