<!doctype html>
<html>
  <head>
    <style>
      [part=one] {
        color: blue;
      }
      [part=two] {
        color: red;
      }
    </style>

  </head>
  <body>
    <div>
      <span part="one">Should be Blue</span> |
      <span part="two">Should be Red</span>
    </div>
  </body>
</html>