<!DOCTYPE html>
<html>
  <head>
    <style>
      input {color: red}
      #two { color: green }
      input[disabled]:not(:enabled) {color: green}
      input:not([disabled]):enabled + #two:enabled {color: red}
    </style>
  </head>
  <body onload='var elem = document.getElementById("one");
                elem.setAttribute("disabled", "disabled");'>
    <input type="button" id="one" value="Should be no red"/>
    <input type="button" id="two" value="Should be no red"/>
  </body>
</html>