How to Hide the "Admin Colors" Admin Menu

function plt_hide_admin_color_schemer_menus() {
	//Hide the "Tools → Admin Colors" menu.
	remove_submenu_page('tools.php', 'admin-color-schemer');
}

add_action('admin_menu', 'plt_hide_admin_color_schemer_menus', 11);

Where do I put this code?