THis gist is for this stack question: http://wordpress.stackexchange.com/questions/180782/theme-style-different-when-user-not-logged-in

enqueue-styles-by-status

<?php
function theme_name_scripts() {
  if( is_user_logged_in() ){
	  wp_enqueue_style( 'style-logged-in', get_stylesheet_uri(). '/css/logged-in.min.css', array(), '1.0.0' );
	}else{
	  wp_enqueue_style( 'style-logged-out', get_stylesheet_uri(). '/css/logged-out.min.css', array(), '1.0.0' );
	}
}

add_action( 'wp_enqueue_scripts', 'theme_name_scripts' );