Legacy. Hermann Ebbinghausâ lasting contributions to the field of psychology are multiple. In addition to being the first psychologist to study areas of human learning and memory, Ebbinghaus contributed greatly to the establishment of experimental psychology.
This includes dimming the display slightly, stopping Mail push and fetch, turning off background app refresh, turning off Hey Siri, and a few other iOS features. By turning these features off, the battery life of the iPhone is extended dramatically, and when Low Power Mode is enabled the iPhone battery icon is yellow to demonstrate this.
Your iPhone battery turns yellow as soon as you tap Turn On. Low Power Mode automatically turns off when you recharge your iPhone battery past 80%. Your iPhone battery is yellow because Low Power Mode is turned on. To change it back to normal, go to Settings -> Battery and tap the switch next to Low Power Mode.