JSFiddle - React, Tailwind, and code Playground

HTML

<div style="float: left;">
    <div class="space">&nbsp</div>
    <div class="box">&nbsp</div>
    <div class="box">&nbsp</div>
    <div class="space">&nbsp</div>
    <div class="box">&nbsp</div>
    <div class="box">&nbsp</div>
    <div class="box">&nbsp</div>
    <div class="box">&nbsp</div>
    <div class="space">&nbsp</div>
    <div class="box">&nbsp</div>
    <div class="space">&nbsp</div>
    <div class="box">&nbsp</div>
    <div class="box">&nbsp</div>
    <div class="space">&nbsp</div>
    <div class="box">&nbsp</div>
</div>

CSS

.box {
    background-color: yellow;
    border-left: 1px solid black;
    border-top: 1px solid black;
    width: 10px;
    float: left;
}
.space {
    background-color: none;
    border-left: 0px solid black;
    border-top: 0px solid black;
    width: 20px;
    float: left;
}

.box + .space
{
    border-left: 1px solid red;
}