Refactoring brand.scss file

Problem/Motivation

If you wanna set the color from the color theme settings to the new element, you need to add this element and color to the `branch.scss` file

Steps to reproduce

N/A

Proposed resolution

Set all colors from the theme settings to the CSS variables.
Remove all elements from the brand.scss file and add CSS variables to the elements where we have a color from the color theme settings.

Remaining tasks

N/A

User interface changes

Clean up `branch.scss` file.
Set CSS variables to the colors from the color theme settings.

API changes

N/A

Data model changes

N/A