This page is designed to customize the user interface.
See the image below:
In the Color Scheme combo box, you can choose color scheme of the application. 
In the Toolbar Style combo box, you can choose style of toolbars.
If you want list items to be gradiently coloured, select the Colour List Items option and set required color saturation using Saturation slider.
You can see the changes without closing of the dialog box. When you modified any preferences on this page, press Apply button. Select the Autoapplying at Changing option and you shouldn’t press this button each time.