ElvUI skin does not follow the colors of ElvUI
e.g.

Also maybe i could be good to skin buttons as well

e.g.

There is no Issue with that. Another Addon is causing that Issue or you are outdated.

If it follows elvui standard skinning it should be the same background color as set in ElvUI.

Right now its always black.
So in reality in your case:

should be

If it follows elvui standard skinning it should be the same background color as set in ElvUI.

Right now its always black. So in reality in your case: should be

You already posted under my Ticket. And didn't read before posting.

It's impossible Bro. To make it Transparent.
Only Way he could add would be a Color Picker for the Full Color Background that's all.

Version 2.28 now comes without an extra background. :)