Problem:

Colored bars are displayed on the screen, as shown in the following figure.

Cause:

Profile GPU rendering may have been enabled in Developer options.

Solution:

Open Settings, search for and access Profile GPU rendering, then disable Profile GPU rendering.

If this is not the case or this issue occurs when Developer mode is not enabled, back up your data and take your phone and proof of purchase to an authorized Huawei Customer Service Center for assistance.