Mirage2/user_config/usr/share/mirage2/stylesheet.css

.image-view {
    /* background-color: rgba(0, 0, 0, 0.0); */
    /* Dark Bergundy */
    border: 2px solid rgba(56, 56, 56, 1);
}

.button-highlighted {
    background-color: #AB7E45;
}