kleur button wijzigen als andere buttons groen zijn

<style>
.rood  { background: red }
.groen { background: green }
</style>

<form id="formulier">
<button id="GC_POD1" class="rood" type="button">GC_POD1</button>
<table>
  <tr>
    <td><button type="button" class="groen">button 1</button>
    <br><label><input type="checkbox" value="A"> checkbox A</label>
    <br><label><input type="checkbox" value="B"> checkbox B</label></td>
  </tr>
  <tr>
    <td><button type="button" class="groen">button 2</button>
    <br><label><input type="checkbox" value="C"> checkbox C</label>
    <br><label><input type="checkbox" value="D"> checkbox D</label></td>
  </tr>
</table>
</form>

<script>
function allButtonsGreen() {
    var subButtons = document.querySelectorAll("#formulier table button");
    for (var i = 0; i < subButtons.length; i++) {
        if (subButtons[i].className.indexOf('rood') != -1) return false;
    }
    return true;
}
var formObj = document.getElementById('formulier');
formObj.addEventListener("change", function(e) {
    e.preventDefault();
    var gcPod1  = document.getElementById('GC_POD1');
    var gcClass = (allButtonsGreen() == true) ? "groen" : "rood";
    gcPod1.classList.remove("groen", "rood");
    gcPod1.classList.add(gcClass);
});
</script>