static/themes/metro-gray/combobox.css

.combobox-item,
.combobox-group,
.combobox-stick {
  font-size: 12px;
  padding: 3px;
}
.combobox-item-disabled {
  opacity: 0.5;
  filter: alpha(opacity=50);
}
.combobox-gitem {
  padding-left: 10px;
}
.combobox-group,
.combobox-stick {
  font-weight: bold;
}
.combobox-stick {
  position: absolute;
  top: 1px;
  left: 1px;
  right: 1px;
  background: inherit;
}
.combobox-item-hover {
  background-color: #E6E6E6;
  color: #404040;
}
.combobox-item-selected {
  background-color: #84909c;
  color: #fff;
}
.combobox-icon {
  display: inline-block;
  width: 16px;
  height: 16px;
  vertical-align: middle;
  margin-right: 2px;
}