Observe.<ul> <li class="open"> Azul </ ...
Observe.
<ul>
<li class="open"> Azul </ li>
<li class="closed"> Vermelho </ li>
<li class="closed"> Verde </ li>
<li class="open"> Amarelo </ li>
<li class="closed"> Roxo </ li>
</ ul>
Na lista acima o que as regras abaixo fariam?
li.open {list-style: circle;}
li.closed {list-style: disc;}