WordPress | Login customisation

wp-login-styles.php

<?php
// Add the login styles
function add_login_scripts() {
    /**
    * login_enqueue_scripts is the proper hook to use when enqueuing items that
    * are meant to appear on the login page.
    */
	wp_enqueue_style( 'core', get_stylesheet_directory_uri() . '/assets/css/login.min.css', array('login') );
}
add_action( 'login_enqueue_scripts', 'add_login_scripts' );

// If we are changing the login logo, it makes sense to also change the URL
function add_login_logo_url() {
    return home_url();
}
add_filter( 'login_headerurl', 'add_login_logo_url' );

Here's some supporting CSS

body.login {
  background-color: #E4EBF0;
}

body.login div#login h1 a {
  background-image: url(../img/logo.svg);
  background-image: none, url(../img/logo.svg);
  -webkit-background-size: auto 84px;
  background-size: auto 84px;
  width: 122px;
  height: 84px;
}