The solution is actually fairly easy. Qt5 has a tool called
qt5ct that allows us to change some of its settings.
We'll install it with
sudo apt-get install qt5ct -y. For the next step, we need to set a permanent environment variable. This will ensure that all Qt apps will use the custom qt5ct settings. Open up your
~/.profile file and add
export QT_QPA_PLATFORMTHEME=qt5ct. Next up, start qt5ct with
qt5ct in the terminal.
In the first tab, simply switch "Palette" to Custom. You can now change the color scheme to your liking. I can recommend "darker". Once you're done, apply the settings. Start the Qt app of your choice, and enjoy not having your retinas burned out of your eyes.