woocommerce/plugins/woocommerce-blocks/assets/js/base/components/button/style.scss

// Extra classes are added for specificity.
.button.wc-block-button,
.editor-styles-wrapper .button.wc-block-button {
	background-color: #000;
	color: #fff;
	display: block;
	font-size: inherit;
	font-weight: bold;
	padding: $gap-small;
	text-align: center;
	text-decoration: none;
	text-transform: none;

	&:hover,
	&:focus,
	&:active {
		background-color: $black;
		color: #fff;
	}
}