Navigation:  Preferences > Skins page > How to (skins) > How to: change default background color of skinless notes

Right click on program icon appears in system notification area and choose "Preferences" menu item from pop-up menu or click on button on PNotes Control Panel.

When "Preferences" dialog appears, choose "Skins" page.

 

To change default background color of skinless notes click on color chooser and select desired color: