You can adjust the contrast of windows and buttons so that they’re easier to see. This is not the same as changing the brightness of the whole screen; only parts of the user interface will change.
Open the Activities overview and start typing Accessibility.
Click on Accessibility to open the panel.
Switch the High Contrast switch in the Seeing section to on.
Quickly turn high contrast on and off
You can turn high contrast on and off by clicking the High Contrast.on the top bar and selecting