<div id = "first_div">First Div
    <div id = "second_div">Second div
      <div id = "third_div">Third Div</div>
      <div id = "fourth_div">Fourth Div</div>
    </div>
  </div>

div{
  margin: 2em;
  height: 7em;
  text-align: center;
  text-transform: uppercase;
  font-family: Verdana;
  font-weight: 900;
  color: white;
}
#first_div {
        --my_bg: orange;
        background-color: var(--my_bg);
      }

      #second_div {
             background-color: var(--my_bg);
      }

      #third_div {
        --my_bg: green;
        background-color: var(--my_bg);
}
      

      #fourth_div {
        background-color: var(--my_bg);
      }