<!DOCTYPE html>
<html>
  <head>
    <style>
      label {color: red}
      input[checked]:checked:default ~ label {color: green}
    </style>
  </head>
  <body onload='var form = document.getElementById("form");
                var input2 = document.createElement("input");
                input2.setAttribute("type", "checkbox");
                input2.setAttribute("id", "two");
                input2.setAttribute("checked", "true");
                form.insertBefore(input2, form.firstChild);
                var label2 = document.createElement("label");
                label2.setAttribute("for", "two");
                var text2 = document.createTextNode("Should be no red");
                label2.appendChild(text2);
                form.insertBefore(label2, document.getElementById("one"));'>
    <form id="form">
      <input type="checkbox" name="group1" id="one" value="1"/>
      <label for="one">Should be no red</label>
    </form>
  </body>
</html>