Why did Huawei's mobile phone content suddenly turn black?

The content of the mobile phone suddenly turns black, and the process of restoring the original color is as follows:

1, Step 1: First, open the settings on Huawei's mobile phone.

2. Step 2: Click the display and brightness options in the setting interface.

Step 3: Then you can find and click the dark mode in the interface.

Step 4: Next, click the switch button on the right.

5. Step 5: Finally, you can transfer your mobile phone back.