.wpcf7-response-output:empty {
    display: none;
}

.wpcf7-form.sent .wpcf7-response-output {
    background-color: #d4edda !important;
    color: #155724 !important;
    border: 1px solid #c3e6cb !important;
}

.wpcf7-form.invalid .wpcf7-response-output,
.wpcf7-form.unaccepted .wpcf7-response-output {
    background-color: #f8d7da !important;
    color: #721c24 !important;
    border: 1px solid #f5c6cb !important;
}