category archive color problem

On the category archive page (blog), I want to display posts from all categories. I want each post in the archive to be the same but different in color such as background or border. I created a main category(archive page) and added to it (as parent) others with changed background. Only it doesn't work. It works fine for system types in templates but not for color. How to solve this ?
PS. i also did according to this video from YT (official) and it doesn't work for colors or backgrounds either