Partition manager doesn't respect the current theme or color template on kde plasma 5.9.
Well, partition manager runs as root, so it uses root themes. Don't think I can do much at the moment. It is possible for KPM to use user's HOME folder but I was told not to do it for security reason (i.e. it is not a good idea for root program writing files into HOME, you'll end up with root owned files). If you really want, you can still kind of do this by linking (with ln command) /root/.config/kdeglobals to the same file in your home folder.
It is still much better now with version 3.0 than it was before. Distributions that used sudo for kdesu did not have any theming at all. Breeze (theme and icon) is already so much nicer than nothing.