how to stilize title property css

[data-title]:hover:after {
    opacity: 1;
    transition: all 0.1s ease 0.5s;
    visibility: visible;
}
[data-title]:after {
    content: attr(data-title);
    background-color: #00FF00;
    color: #111;
    font-size: 150%;
    position: absolute;
    padding: 1px 5px 2px 5px;
    bottom: -1.6em;
    left: 100%;
    white-space: nowrap;
    box-shadow: 1px 1px 3px #222222;
    opacity: 0;
    border: 1px solid #111111;
    z-index: 99999;
    visibility: hidden;
}
[data-title] {
    position: relative;
}<a href="example.com" data-title="My site"> Link </a> with styled tooltip (bigger and with a different background color, as requested in the question)<br/>
<a href="example.com" title="My site"> Link </a> with normal tooltip