#dom-node {
    width: 100px;
}

.child-node {
    height: auto;
}

.red {
    background-color: red;
}

.green {
    background-color: green;
}

.blue {
    background-color: blue;
}

.red,
.green,
.blue {
    height: 3px;
    border: 1px solid lightgrey;
}