How 2 change glowing color

You can use this CSS code. Put it in Comments > Settings > Styling > Custom CSS Code textarea. Save it, delete all caches and do Ctrl+F5 on front-end:

#wpcomm div.wpd-field-invalid span {
    background: #000000;
    color: #FFFFFF;
}

#wpcomm div.wpd-field-invalid span:after {
    border-right: 8px solid transparent;
    border-left: 8px solid transparent;
    border-bottom: 8px solid #000000;
}