/* necessary to make the embedded editor bg white */
.mceContentBody {
  background:#FFF url('');
}
/* or whatever color you want it to be */
body {
  padding:0;
  margin:0;
  background-color:#CDCDCD;
  font-family:arial,sans;
}

#content {
  background-color:#EFEFEF;
  padding:25px;
  margin:0 auto;
  width:925px;
}