How to add transparency to a value from a HTML input type color field in CSS?
<p>In my CSS I need an color based on user picked color.
The color picked is used with a fixed transparency of 80%.</p>

<p>The following form element will let the user choose a color easily.</p>

<pre><code>&lt;input type=color value=#00ffff&gt; // #00ffff
</code></pre>

<p>But how can I add transparency to it in CSS?</p>

<pre><code>rgba(#00ffff,.8) // doesn't work
</code></pre>

<p><strong>Update</strong>: I specifically asked how to do it in CSS, not in JS. BTW it's for a PHP driven CMS. I don't wanna force JS on users, and I prefer not to write conversion functions in PHP.</p>

<blockquote>
  <p>Probably I have to wait for CSS4 (SASS/LESS like) color functions, or
  for the input type color element to be enhanced with an hsla/rgba
  pattern attribute functionality.</p>
</blockquote>