woocommerce/plugins/woocommerce-blocks/assets/js/editor-components/text-toolbar-button/style.scss

.wc-block-text-toolbar-button {
	align-items: center;

	&.is-toggled,
	&.is-toggled:focus {
		background: $gray-700;
		color: $white;
	}
}
.block-editor-block-toolbar__slot {
	// prevents text toolbar items shrinking to avoid other buttons overlapping.
	flex-shrink: 0;
}