JSFiddle - React, Tailwind, and code Playground

HTML

<h3 id="turn"></h3>

<table>
    <tr>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
    </tr>
    <tr>
        <td class="vLine" onclick="addLine(this)"></td>
        <td class="box" onclick="fillBox(this)"></td>
        <td class="vLine" onclick="addLine(this)"></td>
        <td class="box" onclick="fillBox(this)"></td>
        <td class="vLine" onclick="addLine(this)"></td>
        <td class="box" onclick="fillBox(this)"></td>
        <td class="vLine" onclick="addLine(this)"></td>
        <td class="box" onclick="fillBox(this)"></td>
        <td class="vLine" onclick="addLine(this)"></td>
        <td class="box" onclick="fillBox(this)"></td>
        <td class="vLine" onclick="addLine(this)"></td>
        <td class="box" onclick="fillBox(this)"></td>
        <td class="vLine" onclick="addLine(this)"></td>
    </tr>
    <tr>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
        <td class="hLine" onclick="addLine(this)"></td>
        <td class="gap"></td>
    </tr>
    <tr>
        <td class="vLine" onclick="addLine(this)"></td>
        <td class="box"...

CSS

h3 {
    font-family: Arial;
}
table {
    border-collapse: collapse;
}
.vLine {
    width: 10px;
    height: 60px;
}
.box {
    width: 60px;
    height: 60px;
}
.hLine {
    width: 60px;
    height: 10px;
}
.gap {
    width: 10px;
    height: 12px;
    background-color: black;
}
.vLine:hover, .hLine:hover {
    background-color: black;
}

JavaScript

var playerTurn = "Blue";
changeTurn();
var number = 0;

function addLine(obj) {
    fillBox(obj)
    console.log("Called")

    if (obj.style.backgroundColor != "black") {
        obj.style.backgroundColor = "black";
        changeTurn()
    }
}

function fillBox(obj) {
    var indexPos = Array.prototype.indexOf.call(obj.parentNode.children, obj);

    above = obj.parentNode.previousElementSibling.children[indexPos];
    below = obj.parentNode.nextElementSibling.children[indexPos]
    next = obj.nextElementSibling;
    previous = obj.previousElementSibling;

    above.style.backgroundColor = 'green';
    below.style.backgroundColor = 'green';
    next.style.backgroundColor = 'green';
    previous.style.backgroundColor = 'green';
    if (playerTurn == "Blue") {
        obj.style.backgroundColor = "red";
    } else if (playerTurn == "Red") {
        obj.style.backgroundColor = "blue";
    }
}

function changeTurn() {
    if (playerTurn == "Red") {
        playerTurn = "Blue";
        document.getElementById('turn').style.color = "blue";

    } else if (playerTurn == "Blue") {
        playerTurn = "Red";
        document.getElementById('turn').style.color = "red";
    };
    console.log(playerTurn);
    document.getElementById('turn').innerHTML = playerTurn + "'s Turn";
}