HTML:
<ul>
  <li class="a">Hi-1</li>
  <li class="b">Hi-2</li>
  <li class="b">Hi-3</li>
  <li class="a">Hi-4</li>
  <li class="b">Hi-5</li>
  <li class="b">Hi-6</li>
</ul>
CSS:
 li{
   list-style:none;
 }
.a{
   color:blue;
 }
.b:nth-child(odd){
  color:red;
}
.b:nth-child(even){
  color:violet;
}
I want Hi-2, Hi-5 in red and Hi-3, Hi-6 in violet.