django-admin2/djadmin2/static/themes/bootstrap/css/base.css

.sort_link {
    display: block;
    cursor: pointer;
    color: black;
}

.sort_link:hover {
    color: black;
}

.previous-link a {
    color: gray;
}

.date-drilldown {
    padding-bottom: 0;
    padding-top: 0;
}