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;}