<!DOCTYPE html>
<html>
  <head>
    <style>
      label {color: red}
      input:default + label {color: green}
      input:not(:checked):not([checked]):not(:default) + label {color:green}
    </style>
  </head>
  <body onload='document.getElementById("one").setAttribute("checked", "true");
                document.getElementById("two").removeAttribute("checked");'>
    <form>
      <input type="checkbox" name="group1" id="one" value="1"/>
      <label id="l1" for="one">Should be no red</label><br>
      <input type="checkbox" name="group1" id="two" value="2" checked="true"/>
      <label id="l2" for="two">Should be no red</label>
    </form>
  </body>
</html>