You can find the theme on Github https://github.com/gerard33/dark-th3me.
Edit: The theme is part of the standard Domoticz themes since v3.6745.
You can send a pull request if you found any errors or strange stuff.
And as I am not a developer, you will certainly find some strange stuff in the code

The quickest way to test changes to the theme is via the development console in Chrome (open it with F12).
- choose the Sources tab
- choose acctheme and custom.css
- any changes will be visible directly
- if you want to implement these changes then edit these in domoticz/www/styles/dark-th3me/custom.css
Desktop iPad