JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <script>
    var startRed, startBlue;
    var redscore = 0, bluescore = 0;
    var r = 1, b = 1;
    
    function StartA() {
        startRed = setInterval(function() {
            redscore++;
            document.getElementById("red").innerHTML = redscore;
        }, 3000);
    };
    function StartB() {
        startBlue = setInterval(function() {
            bluescore++;
            document.getElementById("blue").innerHTML = bluescore;
        }, 3000);
    };
    function StopA() {
        clearInterval(startRed);
    }; 
    function StopB() {
        clearInterval(startBlue);
    };
    </script>
    
    <p id="blue">0</p>
    <p id="red">0</p>
    <button onclick="StartA()">Start for Red</button>
    <button onclick="StopA()">Stop for red</button>
    <button onclick="StartB()">Start for Blue</button>
    <button onclick="StopB()">Stop for Blue</button>
</body>