li { background-color : red }
.t1 { background-color : lime }
li.t2 { background-color : lime }
.t3 { background-color : red }

<ul>
  <li class="t1">This list item should have green background because its class is "t1"</li>
  <li class="t2">This list item should have green background because its class is "t2"</li>
  <li class="t2">
<span class="t33">This list item should have green background because 
        the inner SPAN does not match SPAN.t3</span>
</li>
</ul>