<p class="box1">

  Lorem ipsum dolor sit amet consectetur adipisicing elit. Voluptates neque iure atque perferendis harum, excepturi, amet laboriosam nam quidem et eligendi reprehenderit similique eius maiores animi voluptatem error ab in.

</p>

​

<p class="box2">

  Lorem ipsum dolor sit amet consectetur adipisicing elit. Voluptates neque iure atque perferendis harum, excepturi, amet laboriosam nam quidem et eligendi reprehenderit similique eius maiores animi voluptatem error ab in.

</p>

​

​

.box1 {

  color: blue;

  /* Supported browser will show black color here: */

  color: var(--my-color); 

}

​

.box2 {

  color: blue;  

  /* Supported browser will show blue color here: */

  color: var(--my-color, blue);

}