Marius L. J.

Personalise your own website, no matter what theme and what customization options are added by the themes creator.
When active, the plugin will add a new section to your Customize screen entitled Simple Customize, containing input fields for various elements needed to display a new customize option.
You can easily find what you wish to customize by using the Find element button, which will let you point and click in the preview window to find what you are looking for. 
Although no prior knowledge of CSS or HTML is required to use the plugin, basic understanding of CSS will definitely help you make the most out of this plugin, an in turn your own site.
Once you are happy with everything in the options, use the Add element button to have your customize option implemented. 
The CSS will be queued up in such a manner that it will try to be the dominant rule, so assuming the theme doesn’t have any <a href="http://stackoverflow.com/questions/3706819/what-are-the-implications-of-using-important-in-css" rel="nofollow ugc">!important</a> flags on its styling, your own styling will appear.
You are also able to implement 3rd party fonts using the plugins own options page, where you may add manual styling alternatives, as well as create categories for grouping your own styles.
All customizations are theme-specific, this means if you ever change your theme, you will get a clean slate to work off when customizing it. 
Of course, should you ever revert back to your old theme, your previous custom styling will still be there.
Note: You should always be cautious of modifying other peoples work, respect the time and dedication put forth by your themes author.

Simple customize

binarymoon

Bartosz Gadomski

Teydea Studio

WP Custom Login lets you fully customize the WordPress login page to match your brand identity.
Whether you run a single site or a multisite network, this plugin gives you control over every visual element of the login screen — from the logo and background to form fields, buttons, links, and more.
Key benefits:
<ul>
<li>Adjust colors, fonts, spacing, and layout of every login page element without writing CSS.</li>
<li>Add your logo, social media links, and custom footer to create a branded login experience.</li>
<li>Support for multilingual sites with per-language text customization for labels, buttons, and notices.</li>
<li>Works with WordPress multisite networks for consistent branding across all sites.</li>
</ul>
WP Custom Login is a good fit for freelancers, agencies, and organizations that want a professional, branded login page. It includes a live preview in the admin settings, so you can see your changes before they go live.
Learn more at <a href="https://wpcustomlogin.com/?utm_source=WP+Custom+Login" rel="nofollow ugc">wpcustomlogin.com</a>.
<h3>Features</h3>
<h4>Free Features</h4>
<ul>
<li>Body background color — Set a custom background color for the login page.</li>
<li>Custom logo — Replace the WordPress logo with your site icon or a custom image, and configure its link URL and alignment.</li>
<li>Form container styling — Customize the form background color, border radius, padding, box shadow, and alignment.</li>
<li>Label styling — Adjust font size, weight, letter case, spacing, text color, and toggle label visibility.</li>
<li>Input field styling — Set background colors, borders, padding, font, shadow, and placeholder text for normal, hover, and focus states.</li>
<li>Checkbox styling — Apply custom colors to the login form checkboxes and checkmark icon.</li>
<li>Primary button styling — Customize colors, font, size, width, alignment, shadow, and per-language button labels.</li>
<li>Secondary button styling — Configure colors, font, border, and per-language labels for secondary buttons.</li>
<li>Notice and error styling — Set colors for error, notice, and success messages, and add a custom persistent notice with per-language text.</li>
<li>Under-form links — Customize link colors, separator, disable the “Back to” link, or add custom links.</li>
<li>Social media icons — Display up to 23 social media icon links (Facebook, X, Instagram, LinkedIn, YouTube, GitHub, and more), placed before the form, after the form, or in the footer.</li>
<li>Privacy policy link — Show or hide the privacy policy link and set its color.</li>
<li>Language switcher — Show or hide the WordPress language switcher and adjust its icon color and spacing.</li>
<li>Custom footer — Add a footer with configurable text, font, color, and alignment.</li>
<li>Custom CSS — Add your own CSS for additional styling.</li>
<li>Live preview — See your changes in real time within the admin settings page.</li>
<li>Disable autofocus — Turn off the default autofocus behavior on the login form.</li>
<li>Disable error shake — Turn off the shake animation on failed login attempts.</li>
<li>Disable autocomplete — Prevent browsers from auto-filling the login form.</li>
<li>Per-language text — Customize labels, placeholders, button text, and notices for each language on multilingual sites.</li>
<li>“Remember Me” customization — Show or hide the “Remember Me” checkbox and set custom label text per language.</li>
</ul>
<h4>PRO Features</h4>
<ul>
<li><a href="https://wpcustomlogin.com/?utm_source=WP+Custom+Login" rel="nofollow ugc">Pre-designed templates</a> — Choose from 20+ ready-made login page designs and apply them with one click.</li>
<li><a href="https://wpcustomlogin.com/?utm_source=WP+Custom+Login" rel="nofollow ugc">Advanced backgrounds</a> — Use animated gradients, image slideshows, or split-screen layouts as your login page background.</li>
<li><a href="https://wpcustomlogin.com/?utm_source=WP+Custom+Login" rel="nofollow ugc">Post-login redirects</a> — Redirect users to specific pages after login based on their roles.</li>
<li><a href="https://wpcustomlogin.com/?utm_source=WP+Custom+Login" rel="nofollow ugc">Premium support</a> — Get direct support from the development team.</li>
</ul>

WP Custom Login

Not too much, not to little, just right.  Allows for custom logo, font and button, and a little extra CSS if needed.  Based on the size of your logo you will need to adjust the background position and/or margins of the #login but with a few tweaks it looks great.  

goldilocks

Customize the WordPress login screen with your own colors, logo, backgrounds, and form styles.

Simple customize vs WP Custom Login