style based on id html code example

Example 1: how to call an id in css

<style>
  #selector {
  color: red;
}
/* # is id selector */
</style>


<div id="selector">
<p>This is an id</p>
</div>

Example 2: html id

<style>
#grepperHeader {
  background-color: lightblue;
  color: navy;
  padding: 40px;
  text-align: center;
}
</style>

<h1 id="grepperHeader">grepperHeader</h1>