woocommerce/plugins/woocommerce-admin/client/products/product-status-badge.scss

.woocommerce-product-status {
	margin-left: $gap-smaller;
	padding-top: 1px;
	padding-bottom: 1px;
	color: $gray-700;
	border-color: $gray-700;

	&.is-instock {
		color: #00a32a;
		border-color: #00a32a;
	}

	&.is-outofstock {
		color: #cc1818;
		border-color: #cc1818;
	}
}