index.css

@import './list-widget.css';
@import './boards-config-dialog.css';
@import './main.css';
@import './monitor.css';
@import './arduino-select.css';
@import './status-bar.css';
@import './terminal.css';

.theia-input.warning:focus {
    outline-width: 1px;
    outline-style: solid;
    outline-offset: -1px;
    opacity: 1 !important;
    color: var(--theia-warningForeground);
    background-color: var(--theia-warningBackground);
}

.theia-input.warning {
    background-color: var(--theia-warningBackground);
}

.theia-input.warning::placeholder { /* Chrome, Firefox, Opera, Safari 10.1+ */
    color: var(--theia-warningForeground);
    background-color: var(--theia-warningBackground);
    opacity: 1; /* Firefox */
}

.theia-input.warning:-ms-input-placeholder { /* Internet Explorer 10-11 */
    color: var(--theia-warningForeground);
    background-color: var(--theia-warningBackground);
}

.theia-input.warning::-ms-input-placeholder { /* Microsoft Edge */
    color: var(--theia-warningForeground);
    background-color: var(--theia-warningBackground);
}