title: Is custom mixing colors possible in CSS?
body: <p>I have two <code>div</code> with two different transparent, colored backgrounds. The elements overlap one another. </p>
  
  <p>I would like to customize the color in the overlapped area.</p>
  
  <p>For example I mix red and blue with opacity 0.5 and would like the overlapped area to be black. Is it possible? This solution would simplify the implementation of functionality.</p>
  
  <p>For better understanding, example:</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-css lang-css prettyprint-override"><code>.wrapper{
    width: 200px;
    height: 500px;
    background-color: #fff;
    position: relative;
  }
  .box{
    width: 100%;
    position: absolute;
  }
  .box-1{
    top: 0px;
    height: 250px;
    background-color: rgba(181, 226, 163, 0.5);  
  }
  .box-2{
    background-color: rgba(183, 222, 241, 0.5);
    top: 200px;
    height: 300px;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="wrapper"&gt;
    &lt;div class="box box-1"&gt;
    &lt;/div&gt;
    &lt;div class="box box-2"&gt;
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>UPDATE:</p>
  
  <p>The height of the overlap area is unknown, so it is <strong>not an option</strong> to add an element <strong>rigidly</strong> on height <code>50px</code>. Question is about
  <strong>custom mixing colors</strong>.</p>