Version: unspecified (using KDE 4.7.3) OS: Linux In the populer document viewers in KDE (Gwenview and Okular) the empty background is dark-grey which is good. Gwenview also makes the background of the scrollbar dark-grey, so only the handle is visible and to avoid the grey bar being there all the time. Okular, however, does not, and so, especially because I have hidden all other UI elements (statusbar, left pane, menu bar, etc) I still get that grey bar at the right where the scrollbar is. The scroll bar background should be dark-grey as well; maybe copying the code from Gwenview is possible. Reproducible: Always Expected Results: Make the scrollbar background grey to match the background of the window.
I don't think this is a good idea from a UI usabililty point of view. The different colour indicates the area in which a user can click in order to scroll up/down by one screen. Settings of this kind should be system-wide, and not the responsibility of each individual application. Hence, if you want the colour of window background and scrollbar background to be the same, you should make a setting in system settings.