body {

    display: flex;
}

.left {
    background-color: aqua;
}

.left li:nth-child(2n+2) {
    background-color: lightgrey;
}

.right {
    background-color: aqua;
}

.center {
    background-color: aqua;
}

.right li:nth-child(1) {
    border: 3px solid red;
}

.right li:nth-child(5) {
    border: 3px solid red;
}

.right li:nth-child(9) {
    border: 3px solid red;
}

.right li:nth-child(13) {
    border: 3px solid red;
}
.right li:nth-child(even) {
    background-color: lightgrey;
}

.center li:nth-child(2n+2) {
    background-color: lightgray;
}

.center li:nth-child(odd) {
    list-style: "🍪";
}