Apple 7 charging display turns yellow. Why?

The mobile phone system should be ios9. When the power is lower than 20%, it will prompt whether to enter the low power mode. When charging in this mode, the battery will be yellow.

Low battery mode function:

After turning on the low battery mode, it will not affect the call and SMS reception, nor will it affect the information received by the installed APP. But when you turn it on, you will find that the battery is much slower than before.

How to turn on the low battery mode of iPhone7:

1. Enter the settings, find the battery, and click Enter.

2. Turn on the battery, with low battery mode.