Format color of drop-down item bar outline in slicer

[empoweredbi]

Hello, how can I change the color of the gray bar that surrounds slicer items when using the drop-down feature? 

Here is an example: https://freeimage.host/i/B4h2Cx

Note that the formatting options under Items do not appear to change this, as Background only affect the background color of each individual item and Outline gives an outline to each individual item AFTER the drop-down menu has been opened. I want to change the color of the outline surrounding the drop-down menu BEFORE anyone has interacted with it.

Thank you in advance!

[Fowmy · Accepted solution]

@empoweredbi 

Unfortunately, there is no option to change the border colour as you requested. You can create an idea on the feature or vote for one if it already exists.: https://ideas.powerbi.com/ideas/

I also searched in the JSON theme visual properties, but it is there either.