How do I change the visual theme of the panel?
For more comfortable work with the panel, you can change the visual theme.
To change the theme:
In the upper right corner, to the left of the username, click “☼”.
В раскрывшемся меню выберите соответствующую тему:
Light theme;
Dark theme;
System theme – the panel will set the operating system theme.
The panel will change the theme in accordance with the selection.

Example of theme selection