One again it is confusing to categorize this... - It is for digikam, but it is meant to make digikam blend in with the GTK+ Adapta Nokto theme :-D
::: Installation :::
1) Download the *.colors file (... really? :-D )
2) Put it in a "colorschemes" folder which digikam knows about.
It can be:
The last one is where it is at if you are running Solus. I had to create the folder "colorschemes".
3) Start/Restart digikam and pick Adapta-Nokto-Solid-Flat
Screenshot is from digikam running on Solus Budgie, which is my current setup.