(In the screenshot, the colour scheme was labelled "Grey", but that was long before I decided to upload it here)
This was my first attempt at desaturating a Trinity/KDE colour scheme, before I knew I could use Trinity's "KColorChooser" (or the colour picker widget in KDE Plasma) and GIMP's "Desaturate" tool, so I did the desaturation using my own logic, rather than relying on software.
I decided to continue using this colour scheme, even though I also created a properly desaturated copy of it, as this does leave a nice glow on the window decorations compared to that.
Here's a link to the correctly desaturated one: (link coming soon)
This is a Trinity colour scheme, so it won't work in KDE Plasma.
Additional preview image info:
Window decorations: KDE 2 default
Widget theme: QtCurve (default gradients only) made to look similar to KDE 2 default ( https://www.opendesktop.org/p/1214244/ )
UI font: Comic Neue