When do the LEDs on my controller light up?
The player LED on the controller shows the user's player number when the controller is connected to a Nintendo Switch console.
The player LED flashes when the controller is connecting to the console or when the controller's battery power is low.
Controller number (horizontal)
The player LED displays in this way when using the Nintendo Switch Pro Controller, or a Joy-Con in solo horizontal grip.
Controller number list (vertical)
The player LED displays in this way when using Joy-Con controllers in solo remote grip or dual-controller grip.