erpnext/www/book-appointment/index.css

.time-slot {
    margin-bottom: 2em;
    margin-left: 0.5em;
    margin-right: 0.5em;
    border-radius: 0.4em;
    cursor: pointer;
    border: 0.5px solid #cccccc;
    min-height: 75px;
    padding: 0.5em 1em;
}

.time-slot:hover {
    background: #ddd;
}

.time-slot.unavailable {
    background: #CBD5E0;
    cursor: not-allowed;
    color: #718096
}

.time-slot.unavailable .text-muted {
    color: #718096
}

input[type="radio"] {
    visibility: hidden;
    display: none;
}

.time-slot.selected {
    color: white;
    background: #5e64ff;
}

.time-slot.selected .text-muted {
    color: #EDF2F7 !important;
}