Improve UI Usability for buttons and local tasks

Problem/Motivation

Whe working with Opigno 8.x-2.x for the first time it took me quite some time to get used to the UX of Opigno.
Still after some time, the UI has some key aspects that are repeatingsly causing irrittion or making it hard to me to solve tasks.

Many screens with action buttons (maybe to add a group) and local tasks seem to be oddly visually prioritised.

Sure, it's important for many cases that other local tasks are visible as tabs. But here it's only settings / site building.
The action priority on this list for a manager is either
* Add a group
* Search, filter, and edit an existing one
* Switch to the other tasks / tabs

The add button is so much muted, i sometimes feel like it's completely missing. The BG is so light, it doesn't even look like a button and the text feels like its a passive body text.

The situation can be a bit improved by reducting the permissions, but then the List Task / Tab looks still like a button..

Maybe this needs to be moved over to the theme Platon?
(I have many more similar UX points. Will slowly create other issues to discuss them in isolation each.)

Steps to reproduce

Go to admin/structure/groups

Proposed resolution

Change color scheme to make these actions look like a button and put primary emphasis on the add button.

Use some color scheme to indicate that a tab like "List" is active, but don't use primary CTA color for it.

User interface changes

Color schema changes. Maybe other UI changes like button look versus tab / tasks look.