Apple makes it easy to discern the state of your iPhone’s battery, not only with a convenient icon in the Status Bar that depicts the current charge level, but also with unique colors that hint about its current condition. For example, a green battery icon indicates a good charge, while a yellow battery icon means that Low Power Mode is turned on and a red battery icon suggests a low charge.
Apple has used the same colors to depict battery states for as long as I can remember, and so it tends to be somewhat monotonous. Fortunately, a newly released and free jailbreak tweak dubbed Eliza by iOS developer WilsontheWolf provides the Status Bar’s battery icon with a wider range of colors to help it express your current battery state.