The KDE video editor Kdenlive is one of the best Linux video editors available for general users. I’ve used it for many versions both in KDE and other desktops like Xfce. Recently it was updated to version 15.12.2 in Fedora. One of the changes from the former 9.10 version was the conversion to Plasma 5 / QF5. This means it defaults to using the Breeze style.
Unfortunately Kdenlive doesn’t detect or use the GTK settings or even the QT5 setting. The style used is set within the application. I’m not sure why it does this but in my experience it is the only KDE application that does it.
I use a dark theme in Xfce and kdenlive looked way out of place. I tried to set it to use the GTK theme but that meant some elements were dark and some not. it looked a real mess. I needed to install the Breeze theme and then set Kdenlive to use Breeze Dark. ‘dnf install plasma-breeze’ is all I needed to do. Then select Breeze in Settings – Style and Breeze Dark in Theme and in that order too. It still isn’t exactly the same colours as other applications but it is close and that seems to be the best I can do.