eg.css

/* full component */
.button {
  color: red;
  font-family: sans-serif;
  ..etc. etc. 
}

/* or utilities */
.red {
  color: red;
}
.sans {
  font-family: sans-serif;
}
/* more utiliies here */

... Example using both 
<div class="button">Warning</div>
vs
<div class="red sans shadow medium-size">Warning</div>