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.
1 If you do find a red indicator on an iPhone, it means that the device may have been submerged or exposed to water or other forms of liquid over a prolonged period.  Take your iPhone to the nearest service center once you find it to have water damage to prevent serious problems.