admin_print_styles action-hook . WP 2.6.0

Fires when styles are printed for all admin pages.

add_action( 'admin_print_styles', 'action_function_name_5754' );
function action_function_name_5754(){
	// action...
}

In file: /wp-admin/admin-header.php

admin_print_styles

do_action( 'admin_print_styles' );

<?php do_action( 'admin_print_styles' ); ?>

do_action( 'admin_print_styles' );

do_action( 'admin_print_styles' );

do_action( 'admin_print_styles' );

add_filter( 'admin_print_styles', 'wp_resource_hints', 1 );

add_action( 'admin_print_styles', 'print_emoji_styles' );

add_action( 'admin_print_styles', 'print_admin_styles', 20 );