Translations:Workspace Configuration/Desktop Configuration/11/en

From KDE UserBase Wiki

Some applications (Qt4 applications) running under KDE4 do not share the same color scheme as KDE4 applications, have an odd background color, or have white text on white buttons, etc. If you change the palette/color scheme in System Settings -> Appearance -> Colors, the Qt applications you have running become the correct color, but change back once they are restarted.