Tabs Border Styling

[SevenFactors]

Hello 👋

Awesome addon for Firefox. I currently am using Sidebery 5.0.0b31 👍

How to add color and perhaps increase the thickness of the currently selected tab (current in-view tab on the browser)? Is there an universal option within the sidebery's CSS style editor?

I've been tinkering and tweaking Sidebery's style but I can't find the option that directly affects the border/frame color of active tabs/currently-in-view tab. :(

--Please see attached images--
I've come to notice that:
When tabs get colorized, their borders also get colorized.
Tabs that don't belong to any container or gain no color (or perhaps when the gained color is black, the border color is not any lighter tone (gray) than the tabs color.

I would like to be able to set my own active/selected tab border color regardless if said app is set to gain its background color from a container or URL/Domain.

Thank you for you help.