zulip/static/styles/activity.css

.activity_head {
    background-color: aliceblue;
}

.table td {
    padding-top:    2px;
    padding-bottom: 2px;
    white-space: nowrap;
}

.table-striped tr.recently_active td {
    background-color: #afa;
}

.table-striped tr.recently_active:nth-child(odd) td {
    background-color: #9e9;
}

.table-striped tr.long_inactive td {
    background-color: #faa;
}

.table-striped tr.long_inactive:nth-child(odd) td {
    background-color: #e99;
}

td.number {
    text-align: right;
}