WinRar is a very good and mostly used compressing utility. It has so many good features and one of them is THEME CUSTOMIZATION.
You can change the themes of winrar also. Simply click the link below and you will be taken to the theme download page. Select any theme you like and download that. The theme will be downloaded as a compressed file.

How To Install The Theme For WinRar:
To install the theme you have just downloaded as rar file, simply double click and install it. Remember that you don't have to extract the theme file. You have to double click on the file.

How To Apply The Installed Theme In WinRar:
After installing the theme, open WinRar and click Options>Themes>YourInstalledThemeName