title: set background opacity in css
body: <p>I want to make the background of an element semi-transparent in css. I am aware that there is a way to do this using</p>
  
  <pre><code>background-color: rgba(100,100,100,0.5);
  </code></pre>
  
  <p>but I am trying to dynamically create the css in my rails application, and the variable I am using is a hex code. Is there an equivalent to rgba() that will allow me to use my hex code as a parameter?</p>