The LED warning light, which is located in the button on the toothbrush handle, shows different status depending on its colour:
Green: the battery is charged.
Yellow: the battery’s charge level is between 50% and 10%.
Red: the battery’s charge level is low (below 10%).
Flashing blue: the toothbrush is connecting via Bluetooth®.
Solid bright green, then flashing bright green : the firmware of the toothbrush is uploading