I've always used this code in a must-use plugin to remove the whole color schemes section:
remove_action( 'admin_color_scheme_picker', 'admin_color_scheme_picker' );
Unfortunately, with WordPress 6.0 this does not work anymore. I've found that Core's add_action( 'admin_color_... was recently moved from default-filters.php file to the admin-filters.php file, but I am unsure why and how I'd have to update the above snippet to make it work again.
 
                        
For a
remove_action()call to be effective, it needs to be called after the action you want to remove has been added, and before the action runs.WordPress adds the
admin_color_scheme_pickeraction in admin-filters.php and then runs the action in the user-edit.php admin page template.To remove the
admin_color_scheme_pickeraction right before it is called on the user profile page, you can run theremove_action()call using theadmin_head-profile.phphook:Note that the
admin_head-{$hook_suffix}hook fires in the head section for a specific admin page. In the example above replacing$hook_suffixwithprofile.phpin the hook name makes it run on the user admin profile page.