How to change main color of WPL frontend?

You can change the main color of WPL frontend into your desired color using WPL->Settings->UI customizer. The UI customizer feature included in WPL PRO.

If you use WPL Theme28 you can change the main color from the options too but if you don't use both of WPL PRO and Theme28 and you don't want to upgrade, you can change the main color of WPL by adding some custom CSS codes to your (child) theme.