My system is openSUSE 42.1 with Plasma 5.
I have some GTK applications installed as well, and I'm experiencing a rather annoying behaviour from them.
Namely, the tooltips of these apps are almost unreadable, being white text over light grey background, as you can see on the picture
I can't find where and how to change this setting; only non-KDE apps are affected, and not all of them: Gimp, Inkscape, Filezilla are amongst them, while Firefox, Libreoffice, Handbrake display the tooltips in a readable way.
Best Answer
The issue is due to a partial override of GTK colors by means of KDE style.
Open
System Settings > Colors
, deselectApply colors to non-Qt applications
, restart the GTK application (e.g. Gimp). This breaks the feeling that all applications share the same style but tooltips will be again readable in both Qt and GTK applications.