style.css

#input_box textarea {
    border: 2px solid #00796b;
    font-size: 1.1em;
}
#output_box textarea {
    font-size: 1.25em;
    color: #00695c;
    font-weight: bold;
    background: #f0fff0;
    border: 2px solid #388e3c;
}
#classify_btn button {
    background-color: #26a69a !important;
    color: #fff !important;
    font-weight: bold;
}