themes-wordpress/xanadu/style.css

/*
Theme Name: Xanadu
Theme URI: https://wordpress.com/theme/xanadu
Author: Automattic
Author URI: https://automattic.com/
Description: This theme is named after the city in Samuel Taylor Coleridge’s poem Kubla Khan. Literary legend says the poem came to Coleridge in a dream, which he rushed to write down without preamble. Likewise, this design begins in earnest.
Requires at least: 6.0
Tested up to: 6.4
Requires PHP: 5.7
Version: 1.0.2
License: GNU General Public License v2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
Text Domain: xanadu
Tags: one-column, featured-images, full-site-editing, rtl-language-support, theme-options, threaded-comments, translation-ready, wide-blocks
*/

/*
* Control the hover stylings of outline block style.
*/
.wp-block-button.is-style-outline > .wp-block-button__link:not(.has-background):hover {
	background-color: var(--wp--preset--color--primary);
	border-color: var(--wp--preset--color--primary);
	color: var(--wp--preset--color--base);
}