Created attachment 168979 [details] screen shot of the situation I am using LibreOffice on my KDE Neon machine. In Impress the left column of the UI uses the colors of the system in a rather strange way. I attached a screen shot and the plasma color scheme I use. In my opinion the contrast between the white of the "paper" and the background color should never be so small. I am aware that this might not be the most important bug. But just to let you know. In my opinion the work on LO in Plasma is really impressive! The program looks beautiful!
Created attachment 168980 [details] plasma color scheme
When you look at the screenshot attached, take a look at the left vertical panel/pane of the Impress GUI (the one with the slides in it). The color of the "paper" behind the slides (white) is almost the same as the background LibreOffice puts as background in this panel/pane. This looks strange.
*** This bug has been marked as a duplicate of bug 134423 ***