If you want to change user color scheme for all users on your site and change user experience. You can change default admin color scheme without any plugin. You need need to add small code snippet into your theme’s functions.php file. You can find this file in your theme folder.
Open functions.php file and put following code in that file.
There are many wordpress admin related methods and code snippet written in my site. simply use search functionality for more code snippets or check wordpress tutorials section.