[syn]

 optgroup {
 color: #FFF;
 background: #000;
 }
 option {
 color: #000;
 background: #FF6;
 }
 
 <fieldset><legend>Beers of the World</legend><select multiple>
 <optgroup label="Campbelltown">
 <option value="sb21">Springbank 21 yr.</option>
 <option value="sb15">Springbank 15 yr.</option>
 <option value="sb12">Springbank 12 yr.</option>
 <option value="glsc">Glen Scotia</option>
 </optgroup>
 <optgroup label="Highland">
 <option value="rlsr">Royal Lochnager Selected Reserve</option>
 <option value="ob14">Oban 14 yr.</option>
 <option value="ldb10">Lock Dhu Black 10 yr.</option>
 <option value="hp12">Highland Park 12 yr.</option>
 <option value="gm71">Glenmorangie 1971 Vintage.</option>
 </optgroup>
 </fieldset></select>

עוד מצויין גם ב IE וגם בFF.
מתוך: http://www.thescripts.com/forum/thread99814.html