li:nth-child(even) {
    color: red;
}
li:nth-child(7) {
    color: green;
}
li:nth-child(3n+2) {
    color: orange;
}
ol {
    margin-bottom: 25px;
}
.parent {
    display: flex;
    height: 100px;
    color: white;
}
div div {
    flex: 1;
    background-color: blue;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 2rem;
}
div div:nth-child(3n+2) {
    background-color: red;
}
table {
    border-collapse: collapse;
    margin-top: 25px;
}
tr:first-child {
    background-color: #eee;
}
td {
    border: solid 1px black;
    padding: 10px;
    width: 112px;
}
.table-1 tr:nth-child(odd) {
    background-color: #ddd;
}
.table-2 tr:nth-child(4n) {
    background-color: #ddd;
}
.table-3 td:nth-child(3) {
    background-color: orange;
}