My battery has begun to show yellow. What does this mean?
My battery information began to show yellow, both in the settings and the icon on the top of the screen. What does this mean?
iPhone SE, iOS 13
Probably you have enabled Low Power Mode.
Low Power Mode reduces the amount of power that your iPhone or iPad uses when the battery gets low. To turn Low Power Mode on or off, go to Settings > Battery. You can also turn Low Power Mode on and off from Control Center.
Use Low Power Mode to save battery life on your iPhone or iPad