Classik theme for KDE Plasma's Aurorae. Designed to be a refreshed version of the default KDE1 theme.
For details see https://www.pling.com/p/1367676/
If possible, use the binary theme instead at http://github.com/paulmcauley/classik This has better performance, inherits system titlebar colours properly and has an Application Style as well as a Window Decoration so that icons in dockable panels match the titlebar icons.