title: How to change color based on number
body: <p>I have just started to learn coding and I have got a problem now.
  I have made this black circle witch has number inside and it goes higher every time you click it but I would want now that even numbers would be blue and odd numbers red (1=red, 2=blue, 3=red etc.)</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>window.onload = function(){
      var laskuri = document.getElementById('laskuri'); 
      function kasvata() {
          var i =++
          laskuri.innerHTML + i;
  
          asetaTaustaVari();
      }
  
      function asetaTaustaVari() {
  
      }
  
      laskuri.onclick = kasvata;
  
  }</code></pre>
  <pre class="snippet-code-css lang-css prettyprint-override"><code>* {
          box-sizing: border-box;
      }
  
      main {
          text-align: center;
      }
  
      #laskuri {
          width: 300px;
          height: 300px;
          background-color: black;
          color: white;
          margin: 50px auto;
          font-size: 200px;
          padding: 30px 0px;
          border-radius: 50%;
          cursor: pointer;
      }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div id=laskuri&gt;0&lt;/div&gt;
      </code></pre>
  </div>
  </div>
  </p>