Unfortunately so far I have not been able to make that work.
The best effort so far is a combination of a few things. I will illustrate the layers one by one 
0. Plain old IDE
1. Add the Devstart.io already!
2. Apply a “toolbar color scheme”
Using the custom VSDark Theme file linked earlier in this thread will get you started. 
Looking a little darker but the menus are kinda off…
3. The SetTheme addin from ClarionAddins
Grab the SetTheme addin from ClarionAddins and apply the VSBlack theme palette:
NOTE: You need to reboot at this point to get the two theming components to “combine” properly. Once you are back it will look like this:
4. Apply the PropertyGridExtras addin from ClarionAddins
With the PropertyGridExtras addin applied you can right-click on the property grid to bring up a context menu with a few options:
From there you can set things like font and theme also:
5. Round it all off by applying a syntax highlighting scheme
There are a few contributions here on Clarion hub - Share your custom syntax highlighting scheme here!
All combined you can get it pretty close:
I did look into enumerating all the PAD controls and tweaking the backgrounds but there is very specific painting going on in some of them that makes it just not worthwhile without some changes in the internals of the IDE I think.
Hope that helps!
p.s. Thanks to @jbrugger recently for helping me clarify this process