You can easily customize the whole interface to your liking with CSS.

The core.css file contains all the styles, and located in CodeBox/resources/app/assets/css/ on Windows and Linux, and in Contents/Resources/app/assets/css/ on Mac

You should override the the original styles in the custom-styles.css file, because core.css will be overwritten when the application is updated

You can create a custom skin in the following way:

html[skin='4] #wrapper , html[skin='4'] #toolbar-drop { background: white; color: #737373; }

If you want to share your theme, I would be more then happy to include it in the next update

You can enable DevTools for easier styling, just delete the comment from this line in CodeBox/resources/app/main.js

mainWindow.webContents.openDevTools();