Some very nice Ubuntu themes do not display buttons and menus properly for some applications (such as LibreOffice). This may be the case particularly for dark themes which hide certain parts of the Ubuntu window, which may have the same color as an application’s main interface. In this post I will provide you with a quick tip to blend multiple themes for creating a new theme for resolving such issues.
Right click on the desktop and select Change Desktop Background. Go to Theme tab and click on the Customize button.
After that, select controls from a different theme and change colors, window borders, icons or pointers. Once done, click Close, the theme (using Save As), keep a name for your new theme and click Save.
For example, in the below screenshot I have mixed the controls of two separate themes. If you were to every face the problem of a dark theme which is overshadowing applications controls, window borders, etc you can use this tip to resolve the problem.