Right Sidebar - Cannot change the color of the first widget

Hi, I have problems in changing the color of the first widget in my right sidebar.
If I change the position of the first widget on top the colour on top is always light blue. I thought it was related to
The site is still under development, still not crawlable but perhaps you can see a test page and a test post here

https://www.pistakkio.net/blog/test-post/

https://www.pistakkio.net/test-page/

If I shift the first widget it is always light blue.
If you need to access I can give you access, but first of all I would like to know if I make something wrong.