Contact Form 7 - Better basic error style

style.css

.wpcf7-form.invalid .wpcf7-response-output,
.wpcf7-form.unaccepted .wpcf7-response-output {
 border: 2px solid #f7e700;
 background: #f7e700;
 color: #1f1f1f;
 margin: 20px 0 10px;
}

.wpcf7-form.sent .wpcf7-response-output {
 border: 2px solid #398f14;
 background: #398f14;
 color: #fff;
 margin: 20px 0 10px;
}