No its not hard coded, it follows the GTK theme. Perhaps @codebrainz KDE distro didn't put much effort into the GTK themes after GTK3 when all the tools to translate KDE themes to GTK2 would have broken.
Add:
``` .tooltip { background-color: #00ff00; } ```
to `~/.config/gtk-3.0/gtk.css` and get minty green.