Select your most favourite movie series : 
  <select> 

  <option value="">Select an option</option>
  <optgroup label="Action">   
    <option value="">Avengers</option>
    <option value="">Die Hard</option>
    <option value="">Fast &amp; Furious</option>
    <option value="">The Dark Knight</option>
    <option value="">The Karate Kid</option>
  </optgroup>
  <optgroup label="Animation">
    <option value="">Despicable Me</option>   
    <option value="">Ice Age</option>
    <option value="">Kung Fu Panda</option>
    <option value="">Madagascar</option>
    <option value="">The Lion King</option>
  </optgroup>
  <optgroup label="Horror">
    <option value="">Mirrors</option>
    <option value="">Scream</option>    
    <option value="">The Final Destination</option>
    <option value="">The Grudge</option>
    <option value="">The Ring</option>
  </optgroup>
    
  </select>

body,
select,
optgroup {
  font-family: "bookman old style";
  font-size: 12pt;
}

optgroup[label="Action"] {
  background: beige;
}

optgroup[label="Action"]::before {
  background: yellow;
}

optgroup[label="Animation"] {
  background: aliceblue;
}

optgroup[label="Animation"]::before {
  background: lightskyblue;
}

optgroup[label="Horror"] {
  background: mistyrose
}

optgroup[label="Horror"]::before {
  background: red;
}