newsupernova/vendor/magento/module-theme/view/frontend/web/css/validate.css

/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
input.mage-error, textarea.mage-error, ul.mage-error, select.mage-error {
    background: none repeat scroll 0 0 #FAEBE7 !important;
    border: 1px dashed #EB340A !important;

}
div.mage-error {
    background: url("../images/validation_advice_bg.gif") no-repeat scroll 2px 1px transparent;
    clear: both;
    font-size: 0.95em;
    font-weight: bold;
    line-height: 1.25em;
    margin-top: 3px;
    min-height: 15px;
    padding-left: 17px;
    color: #DF280A;
}