You can easily modify this default set by creating your own color array.
<script>CuteEditorColorArray = new Array("#FF0000","#FF9900","#99CC00","#339966","#33CCCC","#3366FF","#800080","#999999","#FF00FF","#FFCC00","#FFFF00","#00FF00","#00FFFF","#00CCFF","#993366","#C0C0C0");</script>
You can also disable the "more colors" option.