JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="box"></div><div class="box"></div><div class="box"></div><div class="box"></div>
    <div class="box"></div><div class="box"></div><div class="box"></div><div class="box"></div>
    <div class="box"></div><div class="box"></div><div class="box"></div><div class="box"></div>
    <div class="box"></div><div class="box"></div><div class="box"></div><div class="box"></div>
</div>

CSS

.container {
    width: 100px;
    height: 100px;
}

.line {
    width: 100px;
    height: 25px;
}

.box {
    width: 25px;
    height: 25px;
    float: left;
}

.box:nth-child(8n+2) {
    background-color: red;
}

.box:nth-child(8n+4) {
    background-color: red;
}
.box:nth-child(8n+5) {
    background-color: red;
}

.box:nth-child(8n+7) {
    background-color: red;
}

.box:nth-child(8n+1) {
    background-color: blue;
}

.box:nth-child(8n+3) {
    background-color: blue;
}

.box:nth-child(8n+6) {
    background-color: blue;
}

.box:nth-child(8n) {
    background-color: blue;
}