Here is the plain javascript code:

javascript:t='<table width=100%>';c=new Array('00','33','66','99','CC','FF');
for(i=0;i<6;i++){for(j=0;j<6;j++){t+='<tr>';for(k=0;k<6;k++){L=c[i]+c[j]+c[k];
t+='<td bgcolor=#'+L+'>'+L+'</td>'}t+='</tr>'}}document.write(t+'</table>');void(document.close())


Here is webpage-ready code:

<!--Start websafe colors code
<script language="Javascript" type="text/javascript">
javascript:t='<table width=100%>';c=new Array('00','33','66','99','CC','FF');
for(i=0;i<6;i++){for(j=0;j<6;j++){t+='<tr>';for(k=0;k<6;k++){L=c[i]+c[j]+c[k];
t+='<td bgcolor=#'+L+'>'+L+'</td>'}t+='</tr>'}}document.write(t+'</table>');void(document.close())
</script>
//-->