Source (link to git-repo or to original if based on someone elses unmodified work): https://github.com/doncsugar/Genome-Spectrum/tree/master/auroraeThemes/spectrumClassic/neutral
This theme colors itself according to your panel (plasma theme colors). This includes a light variant and a dark variant for color schemes that are light or dark, respectively. Features a heavy shadow for focused windows and a light shadow for unfocused windows. Recommended configuration is to uncheck "Use theme's default window border size" and select either "No Side Borders" (better) or "No borders" (best).
As with all Aurorae themes, it is better to have lower blur values to avoid sharp corners on blurred windows.