div.diagrams-render-error {
    border: 4px solid red;
}

span.diagrams-title {
    display: block;
    background-color: darkred;
    color: white;
    font-style: bold;
}

span.diagrams-error-files {
    display: block;
    border: 1px dotted grey;
}

span.diagrams-error-input {
    display: block;
    background-color: lightgray;
}