Here you can adjust the user interface to your preferences.
Under User Interface you can set the brightness of the dialogs and controls. If Activate Black Mode is not selected, the colors are defined by your operating system. Selection Color controls the color of selected items in list fields. If this color is transparent, a default color will be used.
Under Icons you can adjust the appearance of the icons in the toolbars. You can choose between colored and gray, with or without shadows. Additionally, you can adjust the size of icons.