Different back-end colour scheme for the different sites of a multisite

Is it possible to have a different back-end colour scheme selected for the different sites of a multisite?

i.e. “Sunrise” for Site A and “Midnight” for Site B

If it’s not possible for the user to setup could it be enforced through a plugin or the theme?

Add to your functions.php file the following code, this will hook into your admin header section and will place the style you chose accordingly to the matching site.

add_action('admin_enqueue_scripts', 'my_admin_background');

function my_admin_background() {
  wp_enqueue_style(
    'custom-style',
    get_template_directory_uri() . '/css/custom_script.css'
  );
      global $blog_id;
      $color="";
      if ($blog_id == 1) {
         $color="white";
      } elseif ($blog_id == 2) {
         $color="red";
      } elseif ($blog_id == 3) {
         $color="blue";
      } else {
         $color="yellow";
      } 
      $custom_css = "<style> body { background: $color } </style>";
  wp_add_inline_style( 'custom-style', $custom_css );
}