body {
    position: absolute;
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 0;
    height: 100%;
    width: 100%;
}

table {
    border-collapse: collapse;
}

td {
    border: solid 2px;
    height: 50px;
    width: 50px;
    text-align: center;
}

.rosso {
    background-color: red;
}

.blu {
    background-color: blue;
}