Well,

 

For the sake of anyone who might stumble upon this problem in the future:

 

Edit the following file:

CuteSoft_Client\CuteEditor\Dialogs\colorpicker.aspx

 

Use code similar to the following:

 

<br />
<style type="text/css">
  .ph_picker a   {float:left;width:11px;height:11px;font-size:0em;border:1px solid black;margin:2px;display:block;}
  .ph_picker div {float:left;height:11px;vertical-align:middle;}
</style>

<table width="100%">
  <tr>
    <td class="ph_picker">
      <div>Custom Colours:</div>
      <a href="#" title="#ce0815" onclick="document.getElementById('val_v').value = '#ce0815';return false;" style="background-color:#ce0815;"><br /></a>
      <a href="#" title="#444444" onclick="document.getElementById('val_v').value = '#444444';return false;" style="background-color:#444444;"><br /></a>
      <a href="#" title="#aaaaaa" onclick="document.getElementById('val_v').value = '#aaaaaa';return false;" style="background-color:#aaaaaa;"><br /></a>
    </td>
  </tr>
</table>