title: Add alpha channel to hex color declared on css variable
body: <p>Like the title says, i would like to somehow add transparency to a hex color defined in css variable. I have seen solutions in other posts using rgb, but I need  hex.
  Maybe with rgba(), calc() or linear-gradient(), but I didn't reach any result with my attempts.</p>
  
  <p>Can someone help?</p>
  
  <p>I couldn't find any related posts since I am using hex colors and css variables</p>
  
  <p>For 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>:root {
    --blue: #0000ff;
  }
   
  .blue-with-alpha {
    color: var(--blue)66; /* I am trying to achieve something like this */
  }</code></pre>
  </div>
  </div>
  </p>