Classik theme for Aurorae. Designed to be a refreshed version of the default KDE1 theme. I believe these titlebar buttons are more visually descriptive than the Breeze buttons and would make a better default.
Hover colours are inherited from Plasma system colours.
Recommended to go to Plasma 5's Window Decoration settings and untick the "Use theme's default window border size" box, and set borders to "No Borders", to reduce glitches at certain resolutions.