main-navigation.html

<ul class="main-navigation">
  
  <li class="main-navigation__menu-item main-navigation__menu-item--active">
    <span class="main-navigation__menu-item-title">Want this</span>
  </li>
  
    <li class="main-navigation__menu-item main-navigation__menu-item--active">
    <span class="main-navigation__menu-item-title main-navigation__menu-item--active-title">Not this</span>
  </li>
</ul>  

main-navigation.scss

.main-navigation {
  
   &__menu-item {
     
     &--active {
       
       &-title {
         color: red;
     }
     
     &-title {
       color: black;
     }
  }
}