This theme basically involves a small modification in the systemtray.svg of kde's default Oxygen Plasma theme.
The screenshot should make this difference obvious.
If you are not able to install this using the get themes interface. Then download the tarball and extract at the following location:
After that basically use the theme.
increasing the height of the taskbar too much breaks the system tray appearance.
This change was done just for the sake of it and i do not intend to fix the issue as i am not really good at this.